HoLLOWAY. — Studies in the New Zealand Species of Lycopodiuni. 207 



habit of growth of the main stem. In L. voluhile and L. scariosum this has 

 not taken place, but in L. fastigiatum and L. densum the young trailing 

 stem early buries itself in the soil. This also is the manner in which the 

 subterranean habit comes about in the developing plant of certain of the 

 species of the Inundata and Cernua sections. 



The " Foot." — In all the species which belong to the section Clavata 

 the young plant possesses a very large " foot " by which it is attached to 

 the prothallial tissues. This foot evidently functions as an absorbing- 

 organ for a considerable time, for the epithelial cells show the presence of 

 abundant contents even after the sporeling has attained a considerable size. 

 This I have already indicated earlier in this paper in my description of a large 

 surface-growing prothallus of L. voluhile. Miss Wigglesworth (31) suggests 

 that it may even function after the disappearance of the prothallus itself. 

 Lang (24) figures the same epithelial layer in the case of the young plant 

 of L. clavatum. Both Miss Wigglesworth and I have found that a strand 

 of vascular tissue containing both xylem and phloem passes off from the main 

 stele of the plant into the foot. The former has demonstrated this in the 

 case of L. complanatum, illustratmg it with a series of figures, but she states 

 that she did not find this condition in the young plants of L. clavatxim. In 

 a previous paper (16, p. 285-86) I have described the presence of this foot 

 strand in the young plants of L. voluhile, stating that whereas in the smaller 

 plantlets the strand consists of small thin-walled cells with abundant cell- 

 contents, in older plantlets a few tracheides are also present. I also stated 

 in the same place that in the exceptionally large " foot " of L. scariosum 

 only in the sections nearest to the main stele was any small-celled tissue 

 to be seen, and this contained no tracheides, and also that in the case of 

 L. fastigiatum the strand was not developed to the same extent as in 

 L. voluhile. T concluded that " the development of vascular tissue in the 

 foot of the young plant varies in extent in different individuals of the same 

 species, and possibly this is dependent simply upon the size to which the 

 parent prothalli may grow." It is evident, therefore, that in this organ 

 also, as in the form and structure of the prothallus, the species composing 

 the Clavata section are in a condition of plasticity. 



Summary. 



In this paper I have described the variations which I have observed to 

 occur in the main characters of the New Zealand species of Lycopodium, 

 and my aim has been to show that these characters must be regarded as 

 being more or less in a condition of great plasticity. Also, at the risk 

 of being tedious, I have noted, in order to institute comparisons, some of 

 the facts relating to the plasticity of other species of the genus. These 

 variations in form and structure can, of course, be viewe(f either as fixed 

 characters or as characters which are maintained only so long as the 

 controlling external conditions are present. This is a cjuestion which can 

 only be settled by experimental cultivation of the plants and prothall 

 concerned. 



The modern genus shows certain main types of form and structure in 

 accordance with which Baker, and more recently Pritzel, has classified the 

 various species. That the latter's classification is a natural one seems to 

 follow from the fact that these types do not relate to one character only, but 

 that all the main characters of the plant, both gametophytic and sporophytic, 

 are more or less consistently interdependent. The different types of the 

 prothallus have been regarded by some botanists as almost unrelated to 



