212 Transactions. 



fungal tissues the terrestrial subterranean forms of prothallus show greater 

 modification than does the epiphytic form, but, on the other hand, as regards 

 external form the former have probably kept nearer to the ancestral type 

 than have the latter. I will return to this again in discussing the prothallus 

 of the Inundata and Cernua sections. It is quite likely that the immediate 

 ancestral stock of the species which comprise the Clavata section were 

 erect-growing forms which belonged to the Selago cycle of affinity. The 

 stelar anatomy is fundamentally similar throughout, the characteristic 

 differences being readily explained. The adoption of the plagiotropic habit 

 ])resents no great difficulties of explanation, nor does the difference in the 

 form of the strobilus. The presence of paraphyses on the prothallus of the 

 Selago and Phlegmaria sections, while serving to emphasize the fact that 

 these two sections together constitute a natural division of the genus, 

 certainly serves also to distinguish between the prothalli of the Selago and 

 Clavata sections. If this particular character can be considered as being 

 amenable, along with so many of the other characters of the prothallus, to 

 changes in the mode of life, its absence from the clavatum and complanatum 

 types of prothallus will have no phylogenetic significance. But there is no 

 doubt that it is to such small and constant features as this, especially those 

 connected with both the sexual and asexual reproductive processes, that 

 we are often to look for the most reliable indications of affinity or other- 

 wise. On the whole, it is possible to relate the Clavata section with the 

 Selago section, although the degree of relationship is clearly not so close as 

 in the case of the Selago and Phlegmaria sections. In other words, whereas 

 many of the species of the Phlegmaria section may be without much doubt 

 linked up with certain of the modern members of the Selago section, and 

 even with L. Selago itself, the species of the Clavata section have possibly 

 been derived from the Selago stock at an earlier date, and even from forms of 

 that stock not now existing. 



Lastly, we must consider the evidence which is afforded by the 

 variations in the New Zealand species of the Inundata and Cernva sections 

 as to the natural position of this group. These two sections seem together 

 to constitute a natural division of the genus which is just as clearly defined 

 as is the Selago-Phlegmaria division. But there can be no doubt that the 

 I Hundata-Cernua group stands more or less apart from the rest of the genus, 

 its chief distinguishing characters being the mixed type of stelar anatomy, 

 the surface-growing chlorophyll-possessing prothallus, and the protocorm 

 condition of the young sporeling. The species that are included in these 

 two sections would seem to have departed from the primitive erect habit of 

 growth less recently than have even the thoroughly plagiotropic species 

 of the Clavata section, for they show practically no erect stage in the young 

 plant. Moreover, the dichotomous type of branching has been in these 

 sections very little replaced by the monopodial. The cones in L. laterale 

 are laterally placed and are sessile, but they are not infrequently terminal, 

 and the branching of the aerial shoots is dichotomous. L. Drummondii 

 branches monopodially, and so especially does L. cernuiim, more particularly 

 in its aerial shoots, but in the young plants the branching is always 

 dichotomous. The branching of the creeping stem in these sections is 

 never confined to the plane of the ground, as it is in the Clavata section, 

 but the aerial shoots arise dorsally. Thus the plagiotropic habit as seen in 

 this group is different in nature from that in the Clavata section. In a genus 

 in which the main character of the prothallus throughout is a greater or 

 less adaptation to a saprophytic mode of life, the occurrence of a type in 



