The Present Position of Palaeozoic Botany. 173 



filling- its cavity. Externally the meg-asporangiiim is enclosed in an 

 integument, springing from the upper surface of the sporophyll, and 

 leaving only a narrow micropylar opening at the distal end, not at 

 the top as in Lepidocarpon. The integument bears long tentacles, 

 directed forwards, which may have played some part in guiding the 

 wind-borne microspores to the mici'opyle. 



There is thus a general analogy with Lepidocarpon, as regards 

 the essential seed-like features, but the structure in quite different 

 in detail. Of the two the Miadesmia fructification is perhaps the more 

 advanced, for the sporangial wall is less developed than in Lepido- 

 carpon, an indication that the protective function had been more com- 

 pletely taken over by the integument. Microsporophylls , probably 

 referable to the same plant, have been found. They agree with the 

 megasporophylls as regards the insertion of the sporangium, but no 

 integument is developed. 



It is remarkable that seed-like organs should have been found in 

 two genera of Palaeozoic Lycopods so different as Lepidocarpon and 

 Miadesmia, in each of which the character must, no doubt, have 

 arisen independently. We can only conjecture that the circumstances 

 of the time may have been peculiarly favourable to the adoption of 

 the seed-habit. The early development of the prothallus, in the case 

 of Lepidocarpon, makes it very probable that pollination, if not fertili- 

 zation, took place on the parent plant, but we have no direct evi- 

 dence on the subject. One striking difference from a typical seed is 

 the fact that in both genera the whole sporophyll was shed with the 

 magasporangium, and formed part of its investment. Analogies with 

 the achenes and nuts of Angiosperms are too remote to be of ser- 

 vice, and we must admit that in these Palaeozoic Lycopods the parti- 

 cipation of the sporophyll marks a low grade of seed-evolution. In 

 fact it is evident that in every respect the seed-like organs in ques- 

 tion, even if they were functionally seeds, still stand very near the 

 Cryptogamic type. In this they differ strikingly from the seeds of 

 the Pteropsida series, which even in the earliest known examples are 

 already highly differentiated organs, with little trace of their Crypto- 

 gamic origin. 



Though there appears to be no sufficient evidence of any relation 

 between the '"seed-bearing" Lycopods and the higher plants, these 

 curious fructifications are of great interest, for it is only in Lepido- 

 carpon and Miadesmia, and, in a different way, in certain species 

 of Selaginella at the present day, that we are able, as it were, to ob- 

 serve a seed in statu nascendi. 



As regards the relation of Palaeozoic to recent Lycopods, it 

 seems most probable that the latter were derived, for the most part. 



