SIZE OF SEEDS 67 



by the plant itself. In this case, if there were a number of 

 seeds they would only get in one another's way, and hence, 

 perhaps, the fact that the subterranean pods only produce one 

 or two seeds. 



In most species the seeds vary somewhat in size ; but in 

 such cases it would not be conclusive to contrast the produce 

 of large seeds with that of smaller ones, because it might 

 fairly be said that the former were better nourished, and in- 

 herently, perhaps, more vigorous. In Cardamine chenopodifolia 

 of Brazil, however, the seeds from the underground pods are 

 larger than the others, and Grisebach found that they produced 

 more vigorous seedlings. 1 



There are, on the contrary, other considerations which may 

 make it an advantage that the number of seeds produced by 

 a flower should be reduced, as, for instance, in the case of the 

 Composite, where the agglomeration of a number of flowers 

 into a single head, as in the Daisy, and their consequent 

 diminution in size, renders it an advantage that each floret 

 should produce but one seed. 



The species with large seeds may, as already mentioned, 

 be divided into two groups first, those in which the embryo 

 is surrounded by endosperm ; and, secondly, those in which it 

 occupies the whole seed. 



In the former the arrangement of the embryo presents no 

 special difficulties, as the endosperm simply fills up all vacant 

 spaces. In the latter, on the contrary, Nature has to exercise 

 much ingenuity, and adopts various devices to fill up the 

 whole space. 



One plan is to arrange the cotyledons face to face, and 

 then roll them up in a ball. This is adopted, amongst other 

 cases, in the Sycamore (fig. 50), and hence the long strap-like 

 form of the cotyledons. Another is to arrange the cotyledons 

 face to face, and then double them up, as in the Cabbage, 

 Mustard, Eadish (fig. 62, B-D), &c. 



In a third the cotyledons are convolute edgeways, as in 

 Calycanthus. 



In Lepidium sativum the cotyledons are trifid (figs. 4 and 



1 ' Der Dimorphismus der Fortpfl. v. Cardamine chenopodifolia,' Gottinger 

 Nachrichtungen, 1878. 



