One result of the protean character of protoplasm is its different
behavior in different plants, different organs of the same plant or
different phases of the activity of an individual cell. In either
case it can perform its functions only between certain limits of
environment, and it performs them best somewhere between these limits.
For each function and each condition there is what physiologists call
a minimum--below which it is not carried on, a maximum--above which
it has stopped, and an optimum--or most favorable. Just as in the
efficient working of a human factory, power and raw materials are
necessary, and workmen must be onto the job, however favorable the
other conditions of manufacture may be.
The secretion of nectar and the storing of honey are consequently not
quite comparable, for the activities of the honey plant are concerned
with the first, and the activities of the bee are concerned with the
second, though these are largely influenced by what the plant is or is
not doing. This must be remembered always when comparing such records
of honey-storing as Mr. Strong’s careful hive-weighings through a
generation, with Mr. Kenoyer’s quantitative measurements of nectar
secretion.
Nevertheless, the most favoring conditions of nectar secretion and
honey storing agree in a number of respects. Vigorous early development
or the plant puts it in condition to do its share of the work best;
whatever conditions may prevail during what for most plants is a very
short part of the growing season, when it is in bloom. Vigorous early
development of the hive bears the same kind of relation to the final
result. Early honey must be stored before the bees have reached the
full strength of the season, which may have something to do-with the
fact that the bulk of the harvest is gleaned from plants that flower
later or continue to flower for a relatively long time.
Mr. Strong’s observations in Iowa show that over half of the net
increase in honey storage in southern Iowa is made in June, and over
four-fifths in June and July. These are the months when the most
productive nectar plants flower, and the hives have reached the crest
of their speculative activity and are undergoing division by that time.
Physiological studies show that the afternoon temperature for nectar
secretion is high--between 90 and 100 degrees Fahrenheit. Observation
on the hive shows that its workers are at their active best in
moderately hot weather. Mr. Strong’s twenty-nine-year average shows
that over half of the average honey for the year is stored when the
daily maximum is between 80 and 90 degrees, and nine-tenths of it
is stored when the high temperature of the day is between 80 and 90
degrees. Nectar is most abundantly secreted, other conditions being
equal, in warm days following cool nights; bees do not seem usually
to work more actively on such days, though a record day for heather
honey in England began with a frost. Damp air increases the quantity
of nectar, as of the expulsion of water through water pores; but dull,
rainy weather lessens or stops the activity of the bees.
Nuptial nectar is secreted chiefly before or during the period of
sexual maturity of the flowers. Many, like cotton, golden currant and
horse-chestnut, change color as this period of sexual functioning and
maximum nectar secretion passes, and bees often are quick to catch the
signal. Extra-nuptial nectar is secreted in greatest quantity while the
near-by flowers and foliage of the plant are young.
Nectar differs from time to time in quality as well as in quantity.
In damp weather the increased quantity commonly causes a greater
dilution of its content of sugar, and the bees have been shown to
store a greater weight of honey several days after a rainy day than
immediately following it. Though the greater part of nectar is water,
its essential part, for the bee-man, is sugar, chiefly a mixture of two
kinds of sugar, that possess a different molecular arrangement though
containing the same number of carbon, hydrogen and starch atoms, which
causes them to behave differently when examined by polarized light, and
materially affects other of their physical properties.
The flow of the water of nectar seems to be like that of water through
water pores, an infiltration under pressure when root-absorption
is least active and leaf evaporation checked; but thoroughly and
repeatedly washing the glands sometimes puts a stop to it. Beating rain
does this as effectively as experimental washing. Change of position
and closing in dark, rainy weather characterize some flowers, and
keep the rain from washing away their accumulated nectar and checking
its replenishment. This was Sprengel’s explanation of the fringe of
hair on the petals of the wild geranium. In proportion as such nectar
guards are effective, they preserve the supply and contribute to its
continuance, in proportion as rain has opportunity to beat upon the
nectar glands it wastes and may even check the production of nectar.
This stopping of nectar flow by washing away the secretion of the
glands, is connected with the affinity for water of sugars. The flow of
water appears to be started by the osmotic force of the disintegrated
part of the walls of the secreting cells; it is stopped when the
resulting substance has been removed from the outer surface of the
secreting cells.
[Illustration: Stomata on nectariferous tissue of _Xanthoceras
sorbifolio_. Greatly magnified. Copied from Bonnier’s “Les Nectaires.”]
If this were all, unless the degenerating cellulose were replenished
in sufficient quantity there would hardly be such a thing as honey
production. Indeed, some extra-nuptial glands secrete a nectar
containing so little sugar that even ants may not be attracted by
it--as is said to be the case with climbing smartweeds cultivated in
England, though it is not usually true of such plants growing wild
here, where they are at home. Commonly, however, the sugar in nectar is
replenished while the secretion of fluid continues.
The passage out of sugar from a living cell is very different from
the escape of water; the latter may result from pressure on the one
hand or osmotic draft on the other, because the outer protoplasm is
permeable to water but not to sugar. When sugar is secreted, this
protoplasmic layer becomes to a greater or less degree permeable to
the escaping sugar. This is one phase of the activity of the living
protoplasm, for secretion is a vital phenomenon. What greater or less
permeability of protoplasm actually consists in is a matter of theory
rather than observation, but the phenomenon is a subject of observation
and experiment. Alternating warmth and cold, within limits, affect
it; it has its optimum, at a rather high temperature, as well as its
minimum and maximum. Through an adequately permeable membrane, the flow
of either water or sugar may be outwards--as it is in normal secretion,
or inwards--when the secretion is absorbed--as experiments show to be
true under some conditions.
Water for nectar secretion is obtained in the first place through
the roots of the plant and travels from the point of absorption to
the point of secretion. Sugar for nectar secretion is manufactured
within the plant, very close to the point where it is secreted. It is
primarily a product of the carbon-fixing or photo-synthetic activity
that marks green plants as the food-makers of the world. Sugars
appear to be among the earliest-formed of such carbon-containing or
organic substances in the plant; but usually they are changed into
starch for storage, and this is subsequently digested or transformed
into a soluble sugar when the time of its use comes. The cells about
some nectar glands are storage repositories of, sugar; in other cases
they accumulate a reserve of starch, as raw material, before their
activities begin in supplying sugar.
Evidently, back of the nectar-production of a given day or season,
very closely related to its own optimum conditions of temperature and
humidity, lies the earlier vegetation of the nectar-producing plants.
Strength and vigor of growth, a good reserve of stored food from the
year before, or favorable spring season, these would seem logically to
affect the activity of the plant in performing this as well as others
of its functions. Kenoyer’s conclusions, from Strong’s honey-gathering
statistics, give support to this expectation: “There is an evident
alteration between good and poor years,” as in apple production; “a
good year has a rainfall slightly above the average, preceded by an
autumn, winter and spring with more than the average precipitation,”
affording adequate and lasting soil moisture; “a rainy May scarcely
fails to precede a good honey season,” for the same reason, “a cold
winter has no detrimental effect on the yield of the succeeding
season, but a cold March reduces it,” through preventing a fair early
growth of the honey plants; “a winter of heavy snowfall, in the great
majority of cases, is followed by a larger honey yield,” because of
its contribution to the soil moisture and the protection afforded the
plants during their hibernation.
Of these conclusions, most bear directly on the conditions favorable
for nectar secretion by the plants; some bear as directly on those
favorable for the wintering in prime condition of the bees. Honey
production rests upon both, not only in June and July and on individual
days in those months of greatest honey storage, but on preceding days
and months of preparation. Perhaps the suggestion may be made, even
that it goes much further back, through long centuries of selective
evolution, side by side, of nectar-yielding plants and honey-storing
insects, gradually coming into mutually helpful harmony.--William
Trelease, University of Illinois. American Bee Journal, January, 1920.
PIGEON BERRY, see Buckthorn.
PIGEON CHERRY, see Wild Cherry.
PIN CLOVER or FILAREE (Erodium cicutarium).
The pin clover, or alfilaria, or filaree, is widely distributed in the
Old World, and in this country has been naturalized from Europe. It is
especially well known on the Pacific Coast from British Columbia to
southern California. There it is said to be one of the most valuable
wild pasture plants.
[Illustration: Fig. 110. Filaree or pin clover.]
It is also called pin grass and heron’s bill. It has a long period of
bloom, beginning in February or March in California, and in some places
continuing through the summer. It produces an abundance of pollen and
considerable honey of good quality. In Gray’s botany it is listed as
“storksbill,” and is mentioned as scarce in New York and Pennsylvania.
It is recorded as occurring in Alabama, where it apparently was carried
with railroad ballast. June is given as the blooming period in the
vicinity of Mobile.
It is also known in several places in Connecticut, where it is said to
bloom in May and June. Professor Pammel states that it is abundant in
the dry soils in the Salt Lake basin and from Colorado to Texas. The
seeds cling to the wool of sheep and this aids in its wide distribution.
Figure 110 shows the plant with blossom and seed pod. It is from the
peculiar shape of the latter that it gets the name of “storksbill” and
“heron’s bill.”
PINE (Pinus).
Occasionally honeydew is reported from the pine trees. The following
references are typical of those to be found in current literature:
“We are having a real flow of water-white honeydew from the pine here
in Polk County. It has been on now for two weeks. Bees in general are
in bad condition.”--Luther Presswood, Reliance, Tenn., Jan. 18, 1907.
American Bee Journal, page 98, 1907.
“Large quantities of honey are often secured from pine woods in
certain parts of Germany. The honey is nearly black in color, still
it finds many admirers, and must, therefore, be of better quality
than the honeydew gathered here at times. The Emmendingen Beekeepers’
Society furnishes all the honey for the Grand Duke’s table (in
Karlsruhe), and it is specified that the honey must be this black
honey of the pine woods.”--Bztg. für Schlesw.--Holstein. American Bee
Journal, page 616, 1906.
Similar honeydew is harvested in Switzerland and appears to be also
much prized by the consumers.
PLUM (Prunus).
Plums, both wild and cultivated, are important sources of nectar over
most of the United States. There are twenty or more species which are
native to North America and which are generally known as wild plums.
The blooming period comes early and with other tree fruits they are
of great value as the source of nectar and pollen at a season when
the colonies most need stimulation. The nectar yield is sufficiently
abundant for the bees to store surplus where colonies are strong and
weather conditions favorable. In Sacramento County, California, surplus
is sometimes reported from prunes. There are probably few places where
bees are kept in America where plums of some variety are not present.
[Illustration: Fig. 111. Plum blossoms.]
POINSETTIA (Euphorbia pulcherrima).
The poinsettia is a well-known ornamental plant. It is a shrub, native
to tropical America, grown to a considerable extent for ornamental
purposes in California. The blossoms are small and inconspicuous, but
there is a striking cluster of brilliant red leaves, surrounding the
flowers, which give an impression of flowers.
The nectaries are very conspicuous cups at the side of the blossoms.
Nectar is secreted in abundance, and if the plant was sufficiently
common it would be an important source. The nectar gathers in large
drops.
POISON IVY, see Laurel; also Sumac.
POISON OAK, see Sumac.