SIR J. LUBBOCK — PUYTOBIOLOGICAL OBSERTATIOKS. 



389 



selves by divergence. In this species, also, it is interesting that 

 one or both cotyledons are often bifid. Is it pos^^ible that the 

 multiplicity of the cotyledons in Conifers (fig. 124) can be due 

 to the same cause ? ' 



In Ephedra tbere is a special membrane, "which remains 

 attached to the root, and tlms prevents the testa from being 

 carried up on the tips of the cotyledons. 



The common Cress {Lepidium sativuni) (fig. 4), to which I 

 have already referred, is a very interesting case, for while in the 

 other species, at any rate in the other English species, of the 

 genus the cotyledons are entire, in Lepidium sativum^ on the 

 contrary, each possesses two long, narrow lateral lobes. 



Fig. 125 represents a section through the seed of Z-. gramini- 

 folium J w hich may be taken as representing the ordinary arrange- 

 ment in the genus. The seeds, conforming to the shape of the 



Fig. 124. 



Fig. 12G 



Fig. 125. 



Fig. 124. Seedling o^ Pinus rigida, X 2. 



Fig. 125. Set-tion of seed qI Lejndium graminifoHum^ X 15. 



Fi*^ 126. Section of seed of L. sativum, X 15. 



capsule, are somewhat triangular, with the radicle in the narrow 

 end. The embryo occupies the whole of the seed, there being no 

 perisperm. In L. sativum (fig. 12G) the seed is of the same form, 

 but nearly twice as lar;j;e, and if, therefore, the cotyledons were to 

 occupy the whole additional space, they would become extremely 

 thick. In perispermic seeds this would present no diflBculty, as the 

 additional space would be simply filled by perisperm. In Lepi- 

 diuniy however, this device cannot be resorted to ; the two lobes, 

 however, just fill up the vacancy. 



LINK- Joruy, — BOTANY, TOL. XXII 



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