GENERAL RESULTS— LYCOPSIDA 637 



epiphytic on the larger Lycopods with which it is 

 associated. The affinities of Miadesmia, which in some 

 respects resembles a Selaginella, are not yet deter- 

 mined, but in any case it seems clear that this genus 

 acquired the seed habit on its own lines, and inde- 

 pendently of Lepidocarpon. 



The seed-like organs of these Lycopods, though they 

 may probably have been functionally seeds in the same 

 sense as those of the Pteridosperms, are greatly inferior 

 to the latter in morphological differentiation, and stand 

 much nearer the Cryptogamic type of megasporangium. 

 They are, in fact, the only really " primitive " seeds 

 known to us, and as such are of special interest, though 

 they probably only represent a side-line of evolution. 



As regards the relation of the 'Palaeozoic to the 

 recent Lycopods, only the heterosporous forms of the 

 latter come under consideration, for as yet we know 

 nothing certain of the history of the homosporous 

 Lycopodiaceae. It now seems clear that the genus 

 Selaginella, or types scarcely distinguishable from it, 

 already existed in the Palaeozoic Flora, and that it had 

 no near relation to the arborescent Lepidodendreae. 

 On the other hand, there may well be some connection 

 between the Lepidodendreae and the greatly reduced 

 heterosporous genus Isoetes, which, in the structure and 

 insertion of its sporangia, as well as in anatomical char- 

 acters, has much in common with the Palaeozoic tree 

 Lycopods. In the occurrence of sterile trabeculae in the 

 sporangia of some Lepidostrobi, Professor Bower has re- 

 cognised an interesting point of agreement with Isoetes? 



1 The curious Triassic genus PUuromeia has been regarded as a link 

 between the two groups, but if, as is stated, the sporangia of PUuromeia 



