18 CLASS-BOOK OF BOTANY. 
(These small ex-albuminous ovules should be eeagene ie 
amined after the structure of the seed of the bean has been 
studied.) : 
The fruit, which consists of the matured and 
somewhat dried ovary, is greatly elongated, and 
dehisces by the splitting-away—from below up- 
wards—of two longitudinal valves, the replum 
and the placente: with their attached seeds 
being left. This kind of 2-celled, 2-carpelled 
fruit is called a siliqua,* and is very charac- 
teristic of the group of plants to which the wall- 
flower belongs. | 
Compare with the preceding any of the following 
cruciferous plants :— 
Single Stock (Matthiola sp.). 
Virginian Stock. 
Water-cress (Nasturtium officinale)—Note the lobed 
leaves, the short racemes, and the stamens often fewer 
than six. . 
Cabbage (Brassica oleracea), or any of its varieties. 
Turnip (Brassica rapa), or Rape, or Mustard. 
Observe the seed with its two cotyledons folded along 
. ' their whole length, and with the radicle lying along the 
Fig.12. Sili- back of the fold. If you have not fresh sced of cabbage 
quaoiWall- oy turnip, old seed—put into a cup with a little boiling 
flower, with water and soaked for half an hour—vwill do excel- 
one valve  Jently, 
removed. ? 
94. SHEPHERD'S Purse (Capsella bursa-pastoris). 
This is a very common weed in all cultivated ground, and, 
like many other of our weeds, has been introduced here from 
Britain. | 
Note its two kinds of leaves: the petiolate radical leaves 
are usually pinnately lobed or pinnatifid} (¢.c., their blades 
are deeply cut into laterally), the upper portion being only 
slightly lobed; the sessile cawline leaves are lanceolate in form, 
usually slightly dentate (.e., toothed) on the margins, and 
their bases are prolonged on both sides so as to clasp the 
stem (=amplexicaul{). Note the very small flowers in 
elongated racemes, the parts being similar in number and 
arrangement to other cruciferous plants. The 2-celled ovary 
is obcordates (like an inverted heart), or obcuneate,|| being 
broadly wedge-shaped below, and with a notch or depression 
in the upper margin, in which the minute stigma is placed. 
* Lat. siliqua, a pod or husk, 
} Lat. pinna, a feather or fin; jindo, fidi, &c., I cleave. 
} Lat. amplexor, I embrace; caulis, the stem. 
at. ob, reversed; cor, cordis, the heart. 
: 
§ L 
| Lat. 0b, and cuneus, a wedge. 
| 
