[D] Todd Prof. J. E.: On the Flowers of _Solanum rostratum_ and _Cassia
chamæcrista_, Amer. Nat., vol. XVI, pp. 281-287, 1882. A brief review
of Todd’s paper is given by Dr. P. Knuth, Handbuch der Blutenbiologie,
Leipzig, 1898.
[E] According to Carruth—Carruth, J. H., Catalogue of Plants seen
in Kansas, with additions by Prof. F. H. Snow and Prof. E. Hall—_S.
rostratum_ first appeared in Kansas in 1864. This date probably refers
to eastern Kansas. Dr. S. W. Williston informs the writers that it
appeared around Manhattan in 1860 or 1861.
[F] One specimen observed growing in rich soil back of a feed-store in
St. Joseph, Mo., in early September had a diameter of over seven feet
and a height of three feet. The plant might be considered as normally
developed, having produced apparently the normal number of seed pods,
and so would not be classed with the rank vegetative development which
plants sometimes show when grown in very rich soil.
[G] _S. rostratum_ appears to be better adapted to xerophytic
conditions by its extensive root system than by any adaptation for the
prevention of evaporation of water. When cut down on a warm day, the
plants wilt in a very few minutes. Roots extend down sometimes for more
than three feet, so that the plants generally appear perfectly fresh
when others around are wilted and drying up.
[H] Mueller, Fritz: Two Kinds of Stamens with Different Functions in
the same Flower, Nature, vol. XXVII, pp. 364, 365, 1883.
[I] Experiments for the determination of the fertility of close and
cross-fertilization are always interesting, but are of especial
interest in the case of a plant such as _S. rostratum_, in which,
if the method of pollination described by Professor Todd is the one
actually depended upon, cross-pollination is sometimes possible and
sometimes impossible on the same raceme. Of course, if, as suggested in
the latter portion of this paper, the method of pollination suggested
by Professor Todd is not the only one, these experiments do not have
the interest which they otherwise would.
[J] As will be remarked, the above insects were all taken August 5 and
6. Careful collecting extending over a considerable period of time
would doubtless secure many other forms which visit the plant more or
less frequently.
[K] Meehan, Thomas: On the Fertilization of _Cassia marilandica_, Proc.
Acad. Nat. Sci. Phila., 1886, pp. 314-318.
[L] Meehan, Thomas, _loc. cit._
[M] It must be stated that in a later paper (Robertson, Charles:
Flowers and Insects, V. Bot. Gaz., vol. XV, No. 8, pp. 199-204),
Charles Robertson does not give the same results as those found by
Thomas Meehan. Robertson says: “Two long stamens, one on each side of
the style, furnish pollen for cross-fertilization. They have inflated
anthers which probably have a bellows-like action, like the long stamen
of _Solanun rostratum_ and _Rhexia virginica_.” Meehan states expressly
in his paper that in the case of _C. marilandica_ he was sure no pollen
was ejected, as Todd found for _S. rostratum_, since in the flowers,
which were covered with a gauze bag, the membrane at the apex was never
ruptured when the stamens were ready to fall. Robertson describes the
method of extracting the pollen in _C. chamæcrista_ in a way which is
essentially the same as Todd gives for _S. rostratum_. He then says,
in speaking of _C. marilandica_: “Four small stamens furnish pollen
for the visitors. Bumblebees milk the pollen out of these, using
their jaws, as in the case of _chamæcrista_.” Meehan says: “Nor was
there any draw-out of the pollen, as observed by Professor Todd. It
is abstracted solely through the pores; and, although I could see no
evidence that such was actually the case, I suspect that fertilization
could only occur through some of this extracted pollen escaping from
the insect to the stigma.” It must be noted here that the method which
Meehan describes for the method of opening of the anthers, the pollen
being “abstracted solely through the pores,” does not agree with the
method described by other observers. Leclerc du Sablon, in a paper,
“Recherches sur la Structure et la Dehiscence des Anthers,” in vol. I
of the seventh series of Annales des Sciences Nouvelles, discusses the
anatomical modifications of the anther walls, by which dehiscence is
secured. His observations cover _Cassia cremophilia_ and _Solanum_.
His observations do not cover a sufficient number of species to make
them of the greatest value in deciding the present points. The author
presents, in a condensed form, his results in: Note sur la Dehiscence
des Anthers, La Belgique Horticole, vol. XXXIV, pp. 148-150, 1884.
Robertson says, in speaking of the central of the three long stamens:
“Bees, no doubt, force the pollen out of this as they do from the
short stamens.” Meehan says: “I watched a mass of plants containing
eighty-eight flower-stems on the 30th of July, and the same lot for
an hour on the 6th of August, but saw no attempt to get pollen from
the longer anthers or to use them in any way but as a platform. It
would indeed be hardly possible for the bee to stand anywhere so as
to get power to pierce the apical membranes of the longer stamens.
When the flower matured and the anthers were ready to fall they were
examined-the four short ones were empty sacs-the three lower ones
proved that they had not served any purpose to the bees, for they were
full of pollen.”
[N] This, of course, in case, as Meehan states, the large anthers do
not dehisce. Of course the statement loses entirely its significance
if, as Robertson states, the large stamens furnish pollen for
cross-fertilization.
[O] While the experiments made upon artificial pollination were very
limited, it will be seen that the pollen from the large stamen in no
case fertilized over twenty-nine per cent. of the flowers pollinated
from it. These flowers, however, were on the same raceme; so the low
per cent. might be due to this, or to the mechanical manipulation.
The suggestion that the pollen of the large stamen is less fertile
than that of the smaller ones is at least interesting as a working
hypothesis.
[P] Notes on Stamens of Solanaceæ, Bot. Gaz., vol. XV, pp. 103-106,
1890.
[Q] Observations on the number of seeds produced and the surety
of fertilization may be of especial interest, when the wonderful
distribution which this plant has attained in recent years is taken
into consideration. The original habitat of _S. rostratum_ was the
southwestern portion of the United States. It has since spread over
a large part of the United States, in many places being recognized
as a very noxious weed. It is also reported from several European
localities. Reports on the destructiveness of the plant as a weed may
be found in publications of the agricultural departments, as: Dewey,
L. H., A Weed Bulletin, Farmers’ Series, No. 28, U. S. Dept. Agr.;
Pammel, L. H., Two Noxious Weeds, Bull. Iowa Exp. Sta., 1895. L. H.
Pammel,—Distribution of Some Weeds in the United States, especially
_Iva xanthifolia_, _Lactuca scariola_, _Solanum carolineum_, and
_Solanum rostratum_, Proc. Iowa Acad. Sci., 1895, vol. II, pp.
103-127—gives the eastward migration of this weed up to 1895.
[R] The racemes of _S. rostratum_ are produced by a scorpoid sympodial
dichotomy of the branch, in which the racemes represent the alternate
branches. At first the raceme develops much more rapidly than the bud
which is to continue the main stem, and so the racemes, when flowering,
are always well towards the outside of the plant.
[S] Robertson, Charles, _loc. cit._
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