THE LYCOPODS (CLUBMOSSES) 



Compared with this fact the interest of the actual chromosome number is far less, 

 and the imperfection of the assessment of it is perhaps not such a serious deficiency 

 at the present stage of the inquiry 

 as might have been anticipated. An 

 approximate analysis of a polar metaphase 

 in a squash preparation is contained in 

 Fig. 250. Multivalents, if present, cannot 

 easily be recognized or allowed for, but 

 ignoring their possible existence, the 

 analysis records approximately 113 pairs 

 and 37 univalents. The sporophytic 

 chromosome number of L. Selago cannot 

 therefore be less than 260. 



The interpretation of these facts is not 

 at once obvious. In the British species of 

 Lycopodium, with the exception of L. anno- 

 tinum, which almost certainly links up 

 with L. clavatum, the cytological evidence 

 as a whole can only underline their com- 

 plete dissimilarity from one another, and 

 one must recognize in them the represen- 

 tatives of phyletic lines which have been 

 so long separated that their cytological 

 connexion, if it ever existed, has become 

 completely obscured. They seem now to 

 be far more different from each other than 

 are the genera or even groups of genera 

 of the Polypodiaceous ferns. This is per- 

 haps a sign of antiquity. Yet suddenly, 

 in L. Selago, we find a species which is 



behaving like a hybrid that has succeeded in covering up a defective meiotic process 

 by a highly successful reproduction by means of bulbils. Can this really be the 

 case? To investigate it further we need to assemble observations on meiosis not from 

 Britain only but from all over the world. It may be that the British plants are peculiar,* 

 or it may be that under certain conditions failure of pairing may be induced from meta- 

 bolic causes and not from lack of homology among the chromosomes. In that case the 

 undoubted gametophytes which have been found might result from local strains or under 

 metabolic conditions in which pairing was not irregular. Before the idea of hybridity 

 can be accepted some explanation for the sexual prothalli must in any case be found. It 

 would be unwise, at this stage, to prejudge the issue as to what this explanation might be, 

 but if the signs of hybridity are borne out by further study, one may be quite certain, 

 first, that the parent species, wherever they may once have been, are unlikely now to be 



* As this chapter goes to press mention can be made of one observation on a non-British plant. At 

 Storlien in Sweden unpaired chromosomes were seen again in the summer of 1948. 



Fig. 251. Silhouette of Lycopodium annotinum L. from 

 Switzerland. Natural size. This specimen pro- 

 vided a root-tip count. 



252 



