SIR J. LUBBOCK—PHYTOBIOLOGICAL OBSERVATIONS. 83 
nent externally as well as internally in the mature state by a 
deeper brown blotch; radicle inferior. 
The perisperm in the mature seed is copious, firm, pale yellow, 
and homogeneous. There is therefore so far nothing in any way 
analogous to the causes which have led to the existence of the 
lobes in the species previously described. 
The embryo is at first straight; the radicle is stout and ob- 
tuse; the cotyledons ovate obtuse, plano-convex, fleshy, pale 
green, and applied face to face. They grow, however, consi- 
derably ; and when (fig. 169) they meet the wall of the seed they 
Fig. 169. Fig. 170. 
Fig. 169. Tilia vulgaris. Section of seed. x 4. 
Fig. 170. Ditto. Embryo. x8. 
bend back on themselves, and then curve round, following the 
general outline of the seed (fig. 170). If any one will take a 
common tea-cup and try to place in it a sheet of paper, the paper 
will of course be thrown into ridges. If these ridges be re- 
moved and so much left as will lie smoothly inside the cup, it will 
be found that the paper has been cut into lobes more or less 
resembling those of the cotyledons of Tilia. Or if, conversely, a 
piece of paper be cut out into lobes resembling those of the coty- 
ledons, it will be found that the paper will fit the concavity of the 
cup. The case is almost like that of our own hand, which can be 
opened and closed conveniently owing to the division of the five 
fingers. l 
It may be said that the seed of the Sycamore (Acer) is not 
very dissimilar in form to that of the Lime (Tilia); and yet the 
cotyledons are long, narrow, and strap-shaped, while those of the 
