CKUCIFER^E 141 



of the larger, occupying the outside of the curve, must 

 also be the longer. The base of the sinns is really the 

 organic apex of the cotyledons, and the ascending lobes 

 are due to lateral development. When the cotyledons are 

 folded longitudinally the two ascending edges of the lateral 

 lobes are pressed against and conform to the interior of 

 the globular seed, while the organic apex is also pressed 

 against the testa and its further development consequently 

 stopped. Growth then proceeds in a lateral direction as 

 long as there is any unoccupied space, thus determin- 

 ing the peculiar form of the cotyledons as seen in germi- 

 nation. 



All the species of Brassica observed conform closely to 

 the above type, as do also Moricandia hesperidifolia, Car- 

 richtera Vellse, Succovia balearica, Eaphanus sativus, E. 

 maritimus &c. Zilla myagroides (fig. 177) seems to differ 

 slightly, but the seeds from which the seedlings were raised 

 were museum specimens, probably old, and the cotyledons, 

 which were slightly eroded in the sinus, might have been 

 deformed. More decided departures from the type are 

 exhibited in several other genera. Diplotaxis erucoides has. 

 broadly oblong, obtuse, emarginate cotyledons ; in Moricandia 

 arvensis they are obovate or cuneate, and slightly emar- 

 ginate ; while in Orychophragmus sonchifolius they are 

 broadly oblong-ovate and emarginate, the smaller one being 

 more evidently cuneate at the base than the other. All have 

 the cotyledons unequal in size like those of Brassica, and, 

 what is more unusual, they are indistinctly veined in Diplo- 

 taxis erucoides, Moricandia arvensis, and Orychophragmus 

 sonchifolius. 



In the case of Hesperis matronalis the cotyledons are not 

 only unequal in length, but vary also in size and shape. By 

 reference to the illustration (fig. 162) it will be seen that the 

 unsymmetrical condition already prevails in the seed before 

 germination. The seed is oblong and terete with the in- 

 cumbent cotyledons slightly concave longitudinally, and the 

 thin radicle lies in the groove. One cotyledon is nearly as 

 thick as the other plus the radicle. After germination the 

 cotyledons of most seedlings belonging to this species are 



