HoLLOWAT. — Studies in the New Zealand Species of Lycopodiuiii. 233 



intracellular hyphal coils, as it is in the prothalli, but it seems to be always 

 present in an intercellular position in the central tissues of the protocorm. 

 These centrally-placed cells, which show abundant protoplasmic contents, 

 are always roundish in form and are separated from one another, the inter- 

 cellular spaces staining darkly with haematoxylin. The appearance of 

 the fungus in the protocorm is thus in marked contrast to the definite 

 epidermal fungal tissue of the prothallus, in which it occurs in hyphal coils. 

 The hyphae can clearly be traced entering the protocorm through the 

 rhizoids. They seem to cross the outer layers of cells mainly, if not entirely, 

 through spaces between the cells and more especially at their angles, and 

 they are not at all apparent in this zone. But when once one has learned 

 to look for them, both the hyphae and also their " spores " can be seen 

 in the spaces between the cells throughout the whole of the central region 

 of the protocorm (figs. 46, 74, and Plate XV ; see also 7, fig. 61, and pi. 17, 

 fig. 2, and pi. 18, figs. 1, 2). The fungal hyphae can best be studied outside 

 ' the protocorm, around the base of which they form an open mat. They 

 are branched and unseptate. Here, too, the spores are abundant, and it 

 can be frequently and clearly seen that they originate by a length of 

 hyphal thread dividing up into a number of the spores. This also can 

 be seen in the intercellular spaces at the centre of the protocorm. It is 

 certainly a striking fact that the fungus never occupies the cell-cavities 

 in the protocorm. The fungus undoubtedly assists the young plant to 

 become self-nourishing. 



Treub and others have supposed the protocorm to be an organ of 

 high phylogenetic importance. Bower, however, believed it to be a 

 physiological modification, just as is the intraprothallial swelling called 

 the " foot." My study of this organ as it occurs in the three New 

 Zealand species certainly inclines me to accept Bower's suggestion. The 

 Lycopodium plant in all its organs is in such a plastic condition that it is 

 unlikely that any highly primitive structures should have been retained — 

 at any rate, in its vegetative parts.* The different sections into which 

 the modern genus is classified are strikingly in accord with its biological 

 divisions, as Lang, with regard to the prothallus, has pointed out. It 

 might be added that this holds also for the other main organs of the 

 Lycopodium. plant. Each type of prothallus is correlated with a certain 

 type of embryo plant. The protocorm is always associated with the 

 cernuum type of prothallus, and apparently with no other. The compara- 

 tive study of the difterent types of prothallial structure certainly leads 

 one to the conclusion that the cernuum type is the least modified of all, 

 and its chlorophyllous habit especially points to this ; but it does not 

 necessarily follow that the cernuum embryo is also the least modified. 

 The presence of the symbiotic fungus teems to have been the dominant 

 factor in determining the form of the different Lycopodium prothalli, and 

 it is a significant fact that the protocorm is also infested with it. 



* There has quite recently been described by Kidston and Lang (Trans. Roy. Soc. 

 Edin., vol. 52, pt. 3, pji. 603-27, 1920) a small plant from the Devonian of Scotland, 

 which the authors have named Hornia Lignieri, whose basal portion consists of a proto- 

 cormous rhizome. This plant the authors compare with the young plants of Lycopodium 

 cernuum, L. laterale, and L. ramulosum. and with Phylloglossum. As they suggest, the 

 demonstrated presence of the " protocorm " in archaic vascular cryptogams introduces 

 quite a new argument into the discussion concerning the nature and origin of this peculiar 

 organ. However, they also briefly point out {ibid., note at boltf)m of p. 612) that fungal 

 hyphae occur in an intercellular position in the tissues of the rhizome of Hornea. 



