166 Transactions. 



taken at its base. Again, branching of the stem is dichotomous and in no 

 case monopodial. Now, the study of the distribution of the species of these 

 two sections as given by Baker or by Pritzel shows clearly that the terres- 

 trial forms occur, on the whole, in colder regions and the epiphytic forms in 

 warmer regions. It would seem, then, that the evolution of the subgenus 

 Urostachya has been determined largely by climatic conditions. That this 

 is so is seen to be more probable still from the fact that the external form of 

 individual species is in a highly plastic condition, varying greatly according 

 to the habitat. Whether we are to regard the Selago form as having 

 been derived from the Phlegniaria form, or vice versa, must at present 

 remain an open question. It will be decided only by a comparative exami- 

 nation of all the other Lycopodium plant structures, for it involves the 

 question whether the genus as a whole is to be read as a reduction or as a 

 progression series. Especially must it be considered in the light of fossil 

 evidence derived from later geological ages than the Carboniferous. In the 

 meantime, considering that the more complex members of the genus are 

 those which show the greatest adaptation to the environment, the onus of 

 proof must lie upon those who would trace in the genus a general reduction 

 in form rather than a progression. 



In the New Zealand biological region L. varium shows a remarkable 

 variation in form according to locality.* In Plate IX, fig. 1, are illustrated 

 three varieties. That named A is a plant which I have collected from the 

 lower end of the Otira Gorge, where it grows abundantly in clumps on rocks 

 and other exposed terrestrial positions. The Otira Gorge is situated on the 

 western side of the Southern Alps, where the climate is exceedingly moist, 

 at a height of about 1,500 ft. In Part I of these studies (16, pp. 254, 290) 

 I have described the same form of this species as it occurs in enormous 

 clumps on the floor of the excessively wet forest of Stewart Island. The 

 plants are upright in habit, and the strobili characteristically curved. This 

 habit is very similar to that of L. strictum Baker of the mountains of Mada- 

 gascar, which is figured in Engler and Prantl (13, fig. 375). The plant of 

 this particular form A is obviously akin to the typical form of L. Billardieri, 

 differing from it in the rigid upright habit, the smaller size, and the short 

 curved strobili, which are not quite so distinct as and are stouter than those 

 of L. Billardieri. C on the same plate illustrates the same species as it 

 occurs on the Dun Mountain, Nelson, in a drier, more exposed situation, and 

 at a height of 4,000 ft. In this case the strobili in their tetragonous region 

 are only from | in. to 1 in. in length, but the sporangia are continued still 

 farther down the branches in the axils of gradually lengthening leaves. 

 B shows two plants of this species as it occurs on the meadows of the 

 Antipodes Islands. f In this particular variety the plants which occur in 

 clumps stand only about 5 in. or 6 in. in height. They are very sparingly 

 branched, and the fertile tips of the branches are very short and grade into 

 the vegetative regions, as in the case of the form from the Dun Mountain. 

 As well as these three forms of L. varium I have before me material of the 

 same species as it occurs on Campbell Island, which was gathered by the 

 Subantarctic Scientific Expedition of November, 1907. These plants are 



* See Postcript, p. 215. 



1 1 am indebted to Dr. L. Cockayne for specimens of this form. Spirit specimens 

 of L. varium from Campbell Island were kindly supplied me by Dr. Cliarles Chilton 

 from material in the Canterbury College Laboratory. For the herbarium material 

 of the Macquarie Island species, and also for that of most of the species in my collec- 

 tion from localities outside the New Zealand biological region, I am greatly indebted 

 to Ml-. T. F. Cheeseman. 



