298 La ng. — The Prothailus 
at least of the characters upon which the systematist is forced 
to depend are not such as render it probable that the groups 
distinguished by their means will be those expressing common 
descent. So slight are these differences that it may be said 
that there is nothing in the external characters of the 
sporophyte to suggest that Lycopodium is not a natural genus, 
the species of which have come to differ somewhat in habit 
from one another. 
All that need be said here with regard to the geological 
history of the genus, which is unfortunately imperfectly 
known, is to point out that there is sufficient evidence to 
show that even in Palaeozoic times Lycopodineous plants 
of the general habit and size of Lycopodium and Selaginella 
existed along with the larger Lepidodendreae. The com- 
parative anatomy of the stele of the existing species of 
Lycopodium is at present too little known to be available as 
an indication of relationship. It may be hoped that the 
investigations which are at present being made on this subject 
will afford a valuable means of checking the conclusions as to 
affinity drawn from the study of the gametophytes. 
At present our attention will be confined to the evidence 
afforded by the gametophyte which is now known in L . 
cernuum 1 , inundatum 2 , salakense 3 , clavatum 4 , annotinum 5 , 
complanatum 6 , Selago 7 , Phlegmaria 8 , Hippuris 9 , nummulari- 
folium* , and carinatum 9 . Before those of L. complanatum 
and Z. Selago , which have only recently been discovered, 
were known, three types unconnected by intermediate forms 
appeared to exist ; these had been termed the cernuum ) 
Phlegmaria , and annotinum types. The further information 
regarding the earlier stages of the prothalli of L. clavatum 
and annotinum given by Bruchmann, and his description of 
the prothalli of L. complanatum and Selago , necessitates 
1 Treub, Ann. Jard. Bot. Buitenzorg, iv. p. 107; viii. p. 1. 
2 Goebel, Bot. Zeit., 1887, p. 161. 3 Treub, Ann. Jard. Bot. Buit., vii. p. 141. 
4 Bruchmann, loc. cit., 1898. 
5 Fankhauser, loc. cit.; Bruchmann, loc. cit., 1885 and 1898. 
6 Bruchmann, loc. cit., 1898. 7 Ibid. 
8 Treub, Ann. Jard. Bot. Buit., v. p. 87. 9 Ibid. vii. p. 146. 
