There are a good many kinds of Thlaspi, of temperate and arctic
regions: smooth low plants, mostly mountain; root-leaves forming a
rosette; stem-leaves more or less arrow-shaped and clasping; flowers
rather small, white or purplish; sepals blunt; style slender, sometimes
none, with a small stigma; pod flat, roundish, wedge-shaped, or
heart-shaped, with crests or wings.
[Sidenote: =Wild Candytuft, Pennycress=
_Thláspi glaùcum_
=White
Spring, summer, autumn
Northwest and Utah=]
A rather pretty little plant, with several flower-stalks, springing
from rosettes of leaves, dull-green, somewhat purplish and thickish,
smooth and obscurely toothed, all more or less covered with a "bloom";
the flowers small, slightly fragrant, forming clusters less than an
inch across, the white petals longer than the thin, greenish sepals.
This grows on moist, mountain slopes. _T. alpéstre_, of the Northwest,
is similar, but without "bloom."
There are only a few kinds of Dithyrea, grayish, hairy plants,
resembling Biscutella of the Mediterranean, with yellowish or whitish
flowers.
[Sidenote: _Dithýrea Wislizéni_
=White
Summer
Ariz., New Mex., Tex., Okla., Ark.=]
A little desert plant, from six to twelve inches tall, with branching
stems; pale, yellowish-green, downy leaves, about an inch long,
with wavy or toothed margins; small white flowers and funny little
seed-pods, sticking out at right-angles from the stem. This grows at an
altitude of three to four thousand feet and is found in the Petrified
Forest.
There are many kinds of Streptanthus, difficult to distinguish,
smooth plants, often with a "bloom"; stems branching; leaves often
clasping at base, the lower ones usually more toothed or lobed than the
upper. The flowers are very peculiar in shape, not like most Mustards,
but suggesting the shape of a Bleeding Heart flower; the sepals usually
colored like the petals, two or all of them bulging at base, so that
the calyx is broad below and contracted above; the corolla regular or
irregular, the petals purple or white, with claws and narrow, wavy or
crisp borders; the stamens four long and two short, or in three unequal
pairs, the longest pair often united below; the pods long, narrow,
flattish or cylindrical, on a broad receptacle; the seeds flat and more
or less winged. These plants are called Jewel-flower, but the name does
not seem particularly appropriate.
[Illustration: Dithyrea Wislizeni.