12 COMMON CANADIAN WIU> PLANTS. 



ORDER X. CRUCIF'ERJE. (CRESS FAMILY.) 



Herbs with a pungent watery juice, alternate leaves without 

 stipules, and regular hypogynous flowers in racemes or corymbs. 

 Pedicels without bractlets. Sepals 4, deciduous. Petals 4, 

 forming a cross-shaped corolla. Stamens 6, two of them shorter. 

 Fruit a silique, or silicic. (See Chap. IV., Part I., for dissection 

 of typical flower.) The genera are distinguished by the pods 

 and seeds, the flowers in all cases being much alike. The seeds 

 are exalbuniinous, consisting entirely of the embryo, which is 

 folded up in a variety of ways. The radicle may be bent so as to 

 lie against the ed<je of the cotyledons, and the seed when cut 

 through crosswise shows this section : o ; the cotyledons are 

 then said to be accumbent. Or the radicle may be folded against 

 the back of the cotyledon, showing this cross-section : '<^> , in 

 which case the cotyledons are said to be incumbent; and if, 

 besides, being incumbent, the cotyledons are doubled round the 

 radicle, thus : ^=^ , they are then conduplicate. 



Synopsis of the Genera. 



* Pod a silique (much longer than broad). 



1. Nastur'tium. Flowers white or yellow. Pod terete, oblong-linear or 



ellipsoid. Seeds in two rows in each cell, globular, without a wing. 

 Cotyledons aocumbent. 



2. Denta'ria. Flowers white or pale purple. Pod lanceolate, flat. Seeds 



wingless, on broad seed-stalks. Stein-leaves 8 or 3 in a whorl; stem 

 naked below. Root-stock toothed or tuberous. Cotyledons aeoumbent. 

 ?,. Cartlam'iiie. Flowers white or rose-coloured. Pod linear or lanceolate, 

 flat. Seeds wingless, on slender seed-stalks. Stem leafy below. Cotyle- 

 dons accumbent. 



4. Ar'abis. Flowers white or whitish. Pod linear or elongated, flattened, 



the. valves usually with a distinct mid-rib. Stem leafy. Cotyledons 

 accumbent. 



5. Erys'imum. Flowers yellow. Pod linear, distinctly 4-sided. Pedicels 



of the pods diverging from the stem. Leaves simple. Cotyledons 

 incumbent. 



6. Sisym'brium. Flowers yellow. Pods awl-shaped, or 4-6-sided, close 



pressed to the stem, the valves 1-3-nerved. Pods sessile or nearly so. 

 Leaves runcinatc. Cotyledons incumbent. 



7. Bras'sica. Flowers yellow. Pod linear or oblong, nearly terete, or 



4-sided, with a distinct beak extent liny t>, i/mnl th<- <>/</ <;/" tin 

 Cotyledons conduplicate. 



