54 ON SEEDLINGS 



a little above the base, and longitudinal ; raphe ventral, pro- 

 ceeding from the hilum to the apex of the seed; chalaza 

 apical, prominent externally as well as internally in the 

 mature state by a deeper brown blotch ; radicle inferior. 



The endosperm 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 

 obtuse ; the cotyledons ovate, obtuse, plano-convex, fleshy, 

 pale green, and applied face to face. They grow, however, 

 considerably ; and when (fig. 102, A) they meet the waU of the 



PIG. 102. Tilia. A, section of seed, x 4. B, embryo, x 8. 



seed they bend back on themselves, and then curve round, 

 following the general outline of the seed (fig. 102, B). 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 removed 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 cotyledons, 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. 

 It may be said that the seed of the Sycamore (Acer) is not 



