STRUCTURE OF FOSSIL PLANTS 



77 



Fig. 58. Seed 



In the ripe seed the large embryo e practically fills 

 up all the space within the two seed coats c l and c 2 ; 

 endosperm, pollen chamber, &c., have been elimi- 

 nated, and the young ovule is very simple and small 

 as a result of the protection and active service of the 

 carpels in which it is enclosed. Small "spores" 

 form the pollen grains. Typical of living Dicoty- 

 ledons. 



These few illustrations represent only the main divi- 

 sions of an army of structures with an almost unima- 

 ginable wealth of variety which must be left out of 

 consideration. 



For the structures illustrated in figs. 54, 55, and 56 

 we have no name, for their possible existence was not 

 conceived of when our terminology was invented, and 

 no one has yet christened them anew with distinct 

 names. They are evidently too complex in organiza- 

 tion and too similar to seeds in several ways to be called 

 spores, yet they lack the essential element in a seed, 

 namely, an embryo. The term " ovule" (usually given 

 to the young seed which has not yet developed an 

 embryo) does not fit them any better, for their tissues 

 are ripened and hard, and they were of large size and 

 apparently fully grown and mature. 



For the present a name is not essential; the one 

 thing that is important is to recognize their intermediate 

 character and the light they throw on the possible evolu- 

 tion of modern seeds. 



A further point of great interest is the manner in 

 which these "seeds" were borne on the plant. To-day 

 seeds are always developed (with the exception of Cycas) 

 in cones or flowers, or at least special inflorescences. 

 But the "seed" of Lagenostoma (fig. 56), as well as a 

 number of others in the group it represents, were not 

 borne on a special structure, but directly on the green 



