3S8 



SIR J. LrBBOCK — PHTTOBIOLOGTCAL OBSERVATION'S 



and tears asunder the seed-coats at one end, and tlie cotyledons 

 are tlius easily withdrawn." 



May not the narrowness of the cotyledons in EschscJioItzia and 

 their deep fission be due to a similar cause ? The seed is slightly 

 pyriform, and the radicle emerges from the narrower end. It 

 bursts through, the soil in an arch, and instead of leaving the seed 

 behind as usual, the cotyledons carry it up with them. Then the 

 two arms of the cotyledons separate, thus widening tlie orifice 

 and draAving themselves out. 



This suggestion seems to be confirmed by the evidence of 

 Schizopetaloii (figs. 120-123), one of the other few cases wdicre the 



Fig. 123 



Fig. 120. 



F]g. 122, 



Fig. 121. 



Figs. 120-123. Stages in the growth of seedling of 



Schizopetalon Walkeri, X 2|. 



cotyledons are bifid. Here, also, the radicle emerges through a 

 comparatively small orifice, and the seed, from whicb the coty- 

 ledons seem to have some difficulty in freeing themselves, is carried 

 up by the embryo, while eventually the lobes of the cotyledons 

 draw themselves out one by one- In Opuntia lasilaris, again, 

 which differs from O. Labouriiana in having narrow cotyledons, 

 the seed is similarly carried up, and the cotyledons free them- 



