_Mustard Family_
Herbs, rarely somewhat woody, with watery acrid juice, alternate
leaves and racemose or corymbose white, yellow, or pink flowers;
sepals and petals 4; stamens 6, rarely fewer; pistil 1, consisting of 2
united carpels.
Pods short; silicles.
Pod compressed parallel to the partition. =Draba.=
Pod compressed contrary to the partition, ovate;
flowers white. =Thlaspi.=
Pod inflated, obcordate; flowers yellow. =Physaria.=
Pods elongated; siliques.
Pod compressed parallel to the partition.
Valves nerveless; flowers white. =Cardamine.=
Valves 1-nerved; flowers white or pink. =Arabis.=
Pods terete, not at all compressed.
Pods 1½ inches long or more.
Flowers yellow, stigma 2-lobed. =Erysimum.=
Pods less than 1½ inches long.
Leaves grey with fine hairs; flowers white. =Smelowskia.=
Leaves not grey-hairy; flowers yellow or white.
Pubescence of simple hairs. =Sisymbrium.=
Pubescence of forked hairs.
Leaves pinnate or pinnatifid; flowers yellow.
=Sophia.=
Leaves entire or nearly so; flowers white.
=Braya.=
Smooth throughout.
Leaves pinnate or pinnatifid; flowers white.
=Roripa.=
[Illustration: Draba oligosperma Hook. (Nat.) Whitlow-Grass.]
[Illustration: Draba andina (Nutt.) A. Nelson. (⅔ Nat.) Mountain
Whitlow-Grass.]
[Sidenote: =Draba glacialis= Adams.]
Caudex much branched, branches short and slender. Leaves strongly
keeled, ¼—¾ of an inch long, more or less loosely stellate-pubescent,
sometimes ciliate at the base. Scapes slender, ¼—6 inches high, hairy
or nearly smooth; racemes few-flowered; sepals with a few long hairs
or smooth petals ⅛ of an inch long, pale yellow, darker at the base;
pod ¼ of an inch or more long, narrowly oblong, acute at both ends, on
pedicels ¼ of an inch or more long; style distinct.
In dry, exposed stony places throughout the Rockies, flowering in early
spring.
[Sidenote: =Draba oligosperma= Hook.]
Stems much branched from the root, densely tufted at the base. Leaves
erect, linear, obtuse, tapering to the base, stiff, ciliate, with
stellate hairs on both sides, especially toward the apex. Scapes
naked; flowers racemose; calyx smooth or with scattered hairs, petals
white or pale yellow, obovate, ⅛ of an inch or more long, pods short,
nearly orbicular, acute at the apex, more or less rounded at the base,
sparingly short-hairy, ⅛ of an inch long; style ⅓ its length. Alpine
summits and dry ridges throughout the Rockies; flowering in May and
June.
[Sidenote: =Draba andina= (Nutt.) A. Nelson.]
Densely cæspitose. Leaves linear-oblong, obtuse, ⅛ of an inch long
or less, stiff and rigid, densely imbricated, forming numerous small
rosettes: stellate-pubescent on both sides. Scapes slender, 1—2 inches
high, few-flowered, petals pale yellow or white, ⅛ of an inch long;
twice as long as the hairy calyx; pods ⅛ of an inch or less long with
short stiff hairs.
On exposed rocks and alpine summits throughout the Rockies, frequent in
the vicinity of Banff, flowering in May and June.
[Sidenote: =Draba nivalis= Liljb. _Arctic Whitlow-grass._]
Caudex with numerous slender matted branches. Leaves in dense
tufts, oblanceolate, acutish with a rather stout mid-nerve, entire,
white-hairy, with dense stellate pubescence, not at all ciliate or
slightly so near the base, ¼ of an inch long or less. Scapes slender,
hairy, 1—3 inches high, calyx hairy; flowers ⅛ of an inch high, the
white petals slightly exceeding the calyx; pods few, usually smooth,
oblong, acute at each end, ½ of an inch or less long on short pedicels
and with a short stout style and 2-lobed stigma.
On alpine summits and exposed ledges throughout the Rockies; flowering
in June.
[Illustration: Draba glacialis Adams. (⅔ Nat.) Whitlow-Grass.]
[Illustration: Draba aurea Vahl. (½ Nat.) Golden Whitlow-Grass.]
[Sidenote: =Draba lonchocarpa= Rydb.]
Similar to the preceding species but with the leaves obtuse; pods ⅓—⅔
of an inch long, smooth, very narrow and usually more or less twisted,
on slender pedicels ¼—½ an inch long.
In moist or shaded ground, on alpine summits or on ledges, throughout
the Rockies; flowering in June.
[Sidenote: =Draba aurea= Vahl. _Golden Whitlow-grass._]
Pubescent throughout with short stellate hairs; stems rather stout,
erect, frequently several from the same root; leafy, 2—15 inches high.
Leaves entire or few-toothed, oblanceolate or lanceolate, stem leaves
usually narrowed and frequently ciliate at the base, ½—2 inches long.
Flowers bright yellow in an elongated leafy raceme; calyx smooth or
somewhat hairy; petals elliptic, less than ⅛ of an inch long; pods
lanceolate to linear, acute, hairy, often twisted, ¼—½ an inch long on
peduncles half their length.
Frequent in dry open ground at the lower altitudes throughout the
Rockies; flowering in June.
[Sidenote: =Draba incana= L. _Hoary Whitlow-grass._]
Erect, simple, or somewhat branched, leafy, stellate-pubescent
throughout, 6—12 inches high. Leaves lanceolate, oblanceolate or ovate,
¼—1 inch long, acute or obtuse, dentate or nearly entire; flowers
white, ⅛ of an inch or less broad; petals notched, twice as long as
the sepals; pod oblong or lanceolate, acute ⅓—½ an inch long on nearly
erect pedicels about ½ their length.
Throughout the region in moist ravines; flowering during June.
Other species of Draba occur in the region but being neither common nor
striking it is deemed out of place to describe them here.
[Illustration: Physaria didymocarpa (Hook.) A. Gray. (⅔ Nat.)
Bladder-Pod.]
[Illustration: Smelowskia calycina (Desv.) C. A. Meyer. (⅔ Nat.)
Smelowskia.]
[Sidenote: =Thlaspi arvense= L. _Penny-cress._]
Decumbent or erect, 6—12 inches high, simple or much branched above.
Leaves spatulate or oblong, obtuse, obtusely- or runcinately-toothed or
angled. Flowers small, white, in a compact head; pods large, ½ an inch
broad, orbicular or nearly so, strongly winged and compressed.
In moist low ground and waste places throughout the Rockies, flowering
in June.
[Sidenote: =Physaria didymocarpa= (Hook.) A. Gray. _Double
Bladder-pod._]
Densely stellate, canescent, pale green, root long and deep. Stems
decumbent or ascending, slender, simple, 3—12 inches long. Leaves
spatulate, the basal ones obtuse, entire or few lobed, narrowed into
margined petioles: stem leaves nearly sessile, acute, much smaller.
Flowers about ½ an inch broad, light yellow in a close raceme, 2—5
inches long in fruit; pods much inflated and variable, often ½ an inch
thick.
In dry clayey and stony soil and on slopes throughout the Rockies;
flowering in June.
[Sidenote: =Cardamine pennsylvanica= Muhl. _Pennsylvania Bitter-cress._]
Smooth or rarely with a few scattered hairs; stems erect, stout or
slender, 8 inches to 3 feet high, usually much branched, somewhat
succulent, leafy up to the racemes. Basal leaves 2—6 inches long, the
terminal leaflet obovate, ovate or obcordate, usually narrowed at
the base, ¼—¾ of an inch wide, the lateral 4—8 pairs oblong, oval or
obovate, all toothed or some of them entire. Flowers about ⅛ of an inch
broad, white; pods very narrowly linear, ½—1¼ inches long, erect when
mature on ascending pedicels.
In wet shaded places, sparingly throughout the region; flowering during
June and July.
[Sidenote: =Arabis hirsuta= (L.) Scop. _Hairy Rock-cress._]
Stem erect, nearly simple, 1—2 feet high, roughly hairy or nearly
smooth. Basal leaves on margined petioles forming a rosette, obovate or
spatulate, obtuse, denticulate, 1—2 inches long; stem leaves sessile,
clasping by an auriculate base, lanceolate or oblong. Flowers ¼ of an
inch or less long, white, in a strict, elongated raceme; pods narrowly
linear, erect or appressed, 1—2 inches long.
In open grounds throughout the Rockies at the lower altitudes;
flowering in June.
[Sidenote: =Arabis Holboldii= Hornem. _Stony Rock-cress._]
Finely stellately pubescent throughout; stems frequently
several, simple or branched, erect ½—2½ feet high. Root leaves
narrowly oblanceolate, entire, an inch or less long; stem leaves
linear-lanceolate to narrowly oblong, acute, sagittate. Flowers rosy
pink or rarely white, becoming more or less reflexed, ¼ of an inch
long; pods more or less abruptly reflexed, straight or somewhat curved
1½—2½ inches long, very narrowly linear.
On banks and stony slopes throughout the Rockies; flowering in June.
[Sidenote: =Arabis Drummondii= A. Gray. _Drummond’s Rock-cress._]
Slightly glaucous, stems erect; 1—2 feet high. Root leaves narrowly
oblanceolate more or less hairy; the stem leaves oblong or
linear-lanceolate, 1—2 inches long. Flowers white or pinkish, ¼ of
an inch long in a close panicle, elongated in fruit; pods erect when
mature, slender, 1½—3 inches long, obtuse.
In open ground and on slopes throughout the Rockies, flowering in June.
[Sidenote: =Arabis Lyallii= S. Wats. _Lyall’s Rock-cress._]
Low, smooth, throughout, or sometimes more or less stellate-pubescent
below; stem simple, several, or many from the same root. Lower leaves
spatulate or linear-oblanceolate, usually ½—1 inch long, sometimes
longer; stem leaves narrowly lanceolate or oblong, sometimes scarcely
auricled. Flowers rose-colour, ¼ of an inch long; pods erect or
ascending, very slender, straight or nearly so, 1—2 inches long.
Alpine meadows and slopes at the higher elevations throughout the
Rockies, flowering in June and July.
[Sidenote: =Erysimum inconspicuum= (S. Wats.) MacM. _Treacle Mustard._]
Erect, 10—18 inches high, cinereous and rough with 2-parted hairs.
Leaves narrowly linear-lanceolate or oblong-linear, mostly entire,
the root leaves crowded and sometimes repand dentate. Flowers sulphur
yellow in a compact head, elongated in fruit, calyx campanulate, ¼ inch
high, petals ⅓ longer, the blades spreading; pods slender, erect or
nearly so at maturity, 1—2 inches long.
In gravelly places, common on the eastern slopes of the Rockies at the
lower elevations, flowering in June.
[Sidenote: =Smelowskia calycina= (Desv.) C. A. Meyer. _Smelowskia._]
Very variable in foliage, finely stellate-pubescent and usually
cinereous-villous with larger single hairs; caudex stout, branched.
Leaves soft in texture, usually deeply pinnatifid with 2-several pairs
of linear to obovate, obtuse segments. Stems several, 1—6 inches high,
racemes at first dense and corymbose, becoming elongated in fruit.
Flowers white with exserted broad rounded petals ⅛ of an inch or more
long; pods usually lanceolate, tapering to each end.
On alpine summits through the Rockies; not common; flowering in June
and July.
[Sidenote: =Sisymbrium altissimum= L. Tall _Hedge Mustard._]
Erect, 2—4 feet high, freely branching, smooth or nearly so. Lower
leaves runcinate-pinnatifid, petioled, the lobes lanceolate, often
auriculate; upper leaves smaller, short petioled, or usually sessile,
very deeply pinnatifid, the lobes linear or lanceolate, dentate or
entire, the uppermost often reduced to linear, entire bracts. Flowers
pale yellow, ¼ of an inch broad on slender spreading pedicels, pods
very narrowly linear, divergent, 2—4 inches long.
At the lower elevations throughout the region as a weed, especially on
the line of the railway, flowering in July.
[Sidenote: =Sophia intermedia= Rydb. _Western Tansy-Mustard._]
Stems 1—2 feet high, sparingly greyish-puberulent, especially below,
or sometimes nearly smooth, often glandular above; hairs more or less
stellate. Leaves twice or thrice-pinnatifid, the primary divisions
oblanceolate or obovate, divided to near the midrib into linear or
linear-oblong segments, sparingly puberulent. Raceme rather long,
flowers small, less than ⅛ of an inch high; petals yellow; peduncles
diverging sometimes nearly at right angles; pod club-shaped.
Common throughout the Rockies in open places at the lower altitudes,
flowering in June and July.
[Sidenote: =Braya humilis= (Meyer) Robinson. _Northern Rock-cress._]
Erect 4—10 inches high, branching below, sparingly hairy. Leaves
spatulate or oblanceolate, the lower obtuse, 1—2 inches long, narrowed
into a petiole, sharply dentate or rarely entire, the upper smaller,
narrower, often acute. Flowers white or pink ⅛ of an inch or more
broad, pedicels erect, ¼ of an inch long in fruit; pods nearly terete,
narrowly linear, ½—¾ of an inch long, valves finely nerved.
In moist gravelly or stony ground throughout the Rockies at the lower
altitudes, flowering in June.
[Sidenote: =Roripa Nasturtium= (L.) Rusby. _Water-cress._]
Aquatic, smooth, branched, floating or creeping, rooting from the
joints. Leaves odd-pinnate of 3—9 segments, the terminal one larger
than the lateral, all obtuse, ovate or oval or the terminal one nearly
orbicular. Racemes elongated in fruit; flowers white, ⅛ of an inch
or more broad; pod ½—1¼ inches long, spreading and slightly curved
upwards, on pedicels of about their length.
In ditches and shallow pools through the Rockies, especially abundant
at Banff in the warm water at the outlet from the Basin; flowering
through June and July.