HoLLOWAY. — Studies in the Neiv Zealand Species of Lycopodium. 229 



intercelhilar position (figs. 46, 47). In this species the cells wliicli immedi- 

 ately adjoin the epidermal layer are not so clearly differentiated as a 

 " palisade " layer as they are in the prothalli of L. cernuum. In the pro- 

 thallus illustrated in fig. 47 the intercellular fungus which belonged to the 

 upper fungal zone occupied a considerable extent of the tissues of the 

 shaft and had spread well up towards the meristem. I have not observed 

 anything approaching this condition in any of the prothalli of L. cernuum. 

 The terminal processes are filamentous rather than lobe-like, and are to 

 be seen in longitudinal section in figs. 46 and 47. Their characteristic 

 appearance, however, is best seen in general view (7, figs. 13-16, and pi. 17, 

 fig. 3). A group of lateral lobes is shown in fig. 46, there being an 

 archegonium present at their base. 



L. ramulosum. — The internal structure here shows nothing differing at 

 all markedly from that of the other two species described above, except 

 that, as in L. laterale, the " palisade " tissue is not so well developed as in 

 L. cernuum,. A prothallus of the massive type is shown in longitudinal sec- 

 tion in Plate XV. A true median longitudinal section of the basal tubercle^f 

 this same prothallus is given in fig. 69. It will be apparent that this figure 

 corresponds very closely to fig. 39, which shows the basal tubercle in 

 L. cernuum in longitudinal section. The rest of the prothallus is free from 

 fungus, and consists mainly of compact small-celled tissue. The crown 

 of filaments in this prothallus is poorly developed. The structure of the 

 elongated prothallus is shown in fig. 70, a and b. The cell-layer in which 

 the fungus is in an intercellular position is here very limited in extent, and is 

 also little differentiated as a tissue. The lateral generative region is brown, 

 and the filaments are here missing. The apical head of the prothallus 

 bears numerous antheridia (fig. 70, c). Fig. 71 shows in longitudinal section 

 two adjoining fungal areas in an elongated prothallus of much larger build 

 than the one last mentioned, and here it will be seen that the intercellular 

 fungus spreads through a correspondingly greater extent of tissue, in which 

 the cells are certainly arranged more palisade-like. The shaft portion of 

 these elongated prothalli consists of large, elongated cells, but the various 

 generative regions are of small-celled tissue. This is clearly seen in the 

 prothallus shown in fig. 70, this prothallus bearing antheridia only. 



Position of the Meristem. 



In the cernuum type of prothallus the meristem is of a more indefinite, 

 unlocalized nature than in either the epiphytic, cylindrical type or the 

 subterranean, cone-like type. In his figures of very young stages in the 

 development of the prothalli of L. cernuum, Treub shows that, in his 

 laboratory specimens, immediately on germination of the spore, a triangular 

 apical cell is set apart, by whose all-round segmentation a globular mass of 

 cells is formed — the " primary tubercle." However, this method of growth 

 immediately gives place to a filamentous stage in whicli the filament is 

 only one cell wide, new segments being formed by transverse walls appear- 

 ing in the terminal cells of the filament. The filament next thickens by 

 longitudinal walls appearing in all its cells. This also is what happens in 

 L. salal-ense; but there several such filaments are formed from the primary 

 tubercle, although only one proceeds to thicken. 



From my material of the three New Zealand species which belong to 

 this type of prothallus I have certainly found instances in which the spore 

 seems to have given rise at once to a globular mass of cells, but others also 

 in which there is an original filamentous stage. This filament extends at 



