ORIGIN OF KNDOOEXS FRO^I EXOOENS. 497 



form in Carum Bulbocastanum assumes that of the embryo of 

 wheat, as also figured by Hegelrnaier*. 



We thus see why one cotyledon is terminal and the other nearly 

 basal, namely by the arrest of the development of one cotyledon. 



The linear cotyledon described and figured by Irmisch has a 

 prolonged sheath, through an orifice of which the plumule escapes. 

 We thus have the additional feature of a coleoptile characteristic 

 of monocotyledons, just as described in Ranunculus Ficaria. 



There would seem, therefore, to be no fundamental difference 

 between this embryo and that of wheat, excepting in the deep- 

 seated origin of the primary root of the latter and the presence 

 of its sheath or coleorhiza. 



Carum Bulbocastanum and C. Carui are not aquatic plants ; 

 but there are reasons for thinking that these two species as well 

 as other umbelliferous genera characterized by having linear 

 cotyledons and finely dissected foliage may have been so ances- 

 trally. Such are, for example, Cuminum Cyminum, Myrrh is 

 odorata, Meum athamanticum, Scandix Pect en- Veneris ^ and fennel ; 

 as well as the linear-leaved or phyllodinous Aciphylla squarrosa 

 and species of Bupleurum. 



The resemblance of the cotyledons to that of Ranunculus 

 Jieterophyllus is very marked ; while (En an the Phellandrium 

 furnishes both kinds of dissected foliage, the submerged and 

 aerial, and thus shows how the above-named terrestrial plants 

 may have been aquatic at first. 



Drs. (xibelli and Ferrero have lately studied the ovule of Trapa 

 natans, L.f Prom their point of view the mature embryo is to 

 be regarded as an amorphous mass or a true thallome on which 

 is developed a single bud, the plumule. The more general view 

 held is that it is a degraded embryo possessing only a single 

 perfect cotyledon, the second being represented by a minute 

 scale reminding one of a similar scale or lobule in the embryo 

 of some grasses, &c. The authors regard the degradation of 

 the embryo as resembling that which occurs in parasitic and 

 semiparasitic plants such as Orchidece, Orobanche, Cynomorium y 



Vergl. Unters. Entw. dicot. Keirae, cf. fig. 4 b Carum with fig. 39 of wheat 

 on the same plate. The corresponding figures of Sparganium are only partially 

 outlined. 



t " Intorno alio sviluppo dell' ovolo e del seme della Trapa natans, L. 

 1 Malpighia,' v. 1891, p. 156. 



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