SIR J. LUBBOCK—PHYTOBIOLOGICAL OBSERVATIONS. 81 
advantage in enlarging the orifice, and thus securing their exit, 
than they would if they occupied the more usual position. This, 
however, I only throw out asa suggestion which requires further 
investigation. 
When the seed is flattened laterally, the embryo must either be 
narrow or lie with its edges of the cotyledons to the placenta. 
For instance, in Heliophila pilosa var. incisa the seeds (figs. 166 
& 167) agree closely in form with those of Cheiranthus (figs. 90 
& 91, C. Cheiri); they are oblong-obtuse at each end, compressed 
Fig. 166. Heliophila pilosa. Longitudinal section of seed. X 12. 
Fig. 167. Ditto. Transverse section of seed. x 12. 
dorsally, with a notch at one end, and in section are narrow 
elliptic; but while the cotyledons of Cheiranthus are broad, 
in Heliophila they are long and linear. The reason of this 
may be that while in Cheiranthus and other Arabidew the pods 
are flattened dorsally and the cotyledons are accumbent in the 
broad way of the seed (figs. 90 & 91), those of the Sisymbres, to 
which Heliophila belongs, have (figs. 166 & 167) the cotyledons 
incumbent, so that they lie across the seed, and are consequently 
linear. 
Similar eases occur in other Orders, as for instance in Caryo- 
phyllez and Solanes. 
Divided Cotyledons. 
Divided cotyledons are far from frequent ; still in my previous 
memoir I described several cases, and pointed out the causes to 
Which they seemed to me to be due. 
In the Lime (Zilia, fig. 168) we havea different and very inter- 
esting case. 
The cotyledons are broad, foliaceous, rhomboid-subtriangular, 
and 5-lobed, 5-nerved at the base, with the outer and lower pair of 
