HoLLOWAY. — Studies in the New Zealand Species of Lycopodjum. 209 



which are borne on the clavatum and complanatum types of prothallus. In 

 these latter species the prothallus is stil) more deeply buried, and the leaves 

 on the young stem are also no more than scales, so that the prothallus 

 functions as the source of food-supply for a lengthy period. " The size of the 

 foot in the New Zealand epiphytic species can be seen from figs. 11 and 34, 

 the foot being in transverse section in the former figure and in longitudinal 

 section in the latter. There is a well-defined epithelial cell-layer around 

 the periphery of the foot where the latter is in contact with the prothallus, 

 and the outer walls of these epithelial cells are strongly defined, staining 

 darkly. The adjoining prothallial tissue is small-celled and contains abundant 

 protoplasm and darkly-staining nuclei^ extensive cell-division having taken 

 place here contemporaneously with the development of the plant. The 

 central cells in the foot are large, with their long axes directed towards the 

 stem-apex. All of these features, of course, point to the fact that there- 

 is a well-established translocation of food material from the prothallus 

 into the developing plantlet, and that the epithelial layer functions as an 

 absorbing tissue. 



The first root develops comparatively late. It may be recognized as a 

 conical outgrowth at the base of the stem on the side which lies away from 

 the prothallus even before the stem-apex has reached the surface of the 

 soil, but it never seems to develop farther until the first leaves are being 

 produced. Fig. 34 shows the first root in longitudinal section, it being 

 apparent from this figure that the main vascular tissues of the stem lead 

 down bodily into the root, while just a few narrow conducting-elements 

 connect the former with the central tissue of the foot. Fig. 34, which is 

 a drawing of the young plant of L. Billardieri var. gracile, is strikingly 

 similar to the figure which Bruchmann gives of the young plant of L. Selago 

 (1, pi. 7, fig. 43). I have observed a number of ypung plants of the New 

 Zealand epiphytic species in this condition, so that it may be taken as 

 representing characteristically this stage in the development of the young 

 plant and its mode of dependence upon the prothallus in both the Selago 

 and Phlegmaria sections. 



Treub stated that in the young plant of L. Phlegmaria he had found an 

 indication of a swelling which he regarded as a rudimentary protocorm. 

 Bower, however, has questioned this, and Treub's statement has never been 

 established. I have found no indication of a protocorm in any of the three 

 New Zealand species which belong to this section of the genus. In his 

 Origin of a Land Flora Bower says that he regards the Selago and Phlegmaria 

 type of embryo plant as being the primitive type for the genus, as it 

 certainly is the most simple. The clavatum and complanatum type of 

 embryo, he says, is not very dissimilar to it, but has become more modi- 

 fied through the large development of the foot consequent on the deeply 

 subterranean habit of the prothallus. The cernuum-inundatum type of 

 embryo stands rather by itself. The intraprothallial swelling called the 

 " foot " is here practically absent, but instead there is the extra-prothallial 

 swelling which Treub called the " protocorm." Bower and others hold 

 stroijgly that the protocorm is not a primitive character, as Treub "had 

 supposed, but merely a physiological modification. 



Details of the Fungal Symbiont. 

 A symbiotic fungus occurs very commonly throughout the Pteridophyta 

 in the subterranean forms of prothallus, and it has been carefully studied 

 in most of those species of Li/copodium of which the prothalli are known. 



