HoLLOWAY. — Studies in the New Zealand Species of Lycopodium. 299 



position of the xylem and phloem groups in these species is very mixed, 

 and the individual elements cohere loosely together to form the rows 

 and groups. This is most marked in the two species L. cernuum and 

 L. salakense. It has been noted that iu L. cernuum and L. laterale 

 the vascular strand in the very young plant is indefinite in configura- 

 tion, owing to the fact that it is largely made up of the leaf-traces from 

 the neighbouring protophylls and the first-formed leaves. Moreover, in 

 the adult stem of L. cernuum branching takes place not only right and 

 left of the stem, but also from its dorsal side, while in the rhizome of 

 L. laterale there is no regular plane of branching at all. 



Another important variation from the typical stellate or radial 

 vascular cylinder is the arrangement of the xylem and the phloem in 

 more or less parallel plates. This is found in certain plagiotropic species 

 which Pritzel has grouped in the Clavata and Gernua sections. It will 

 be shown below that there are reasons for removing L. clensum and 

 L. voluhile (both of which show the parallel character) from the vicinity 

 of L. cernuum. Beside the two species just mentioned, L. scariosum 

 and L. fastigiatum both show the parallel arrangement of their vascular 

 tissues, and Jones (13) has enumerated various other plagiotropic species 

 which do the same, all of which Pritzel has grouped in his section 

 Clavata. This parallel character is due probably to the branching being 

 restricted to the plane of the ground. In these plagiotropic species the 

 growth in length of the main axis is unlimited and the growing apices 

 are broad, so that the vascular cylinder at each brandling is of the full 

 size. Thus the parallel disposition of the vascular tissues, when once 

 initiated, naturally persists. 



The adventitious roots bear a marked resemblance to the rhizome in 

 the plagiotropic species not only in vascular structure, but also in other 

 characters. There is the same differentiation of the cortical tissues in 

 both. The more deeply growing almost naked rhizome of L. ramu- 

 losum is interesting as suggesting an intermediate form between the 

 typical scaly rhizome and the leafless adventitious root. The long aerial 

 adventitious roots of L. voluhile also might be termed either stems or 

 roots. 



The New Zealand species of Lycopodium, vary markedly from one 

 another in the differentiation both of their vascular and of their cortical 

 tissues. The xylem elements may be either all of one kind, as also the 

 phloem, or there may be a marked differentiation into vessels and 

 accompanying parenchyma. Generally speaking, it is in the plagio- 

 tropic species that this differentiation is found in the greatest degree. 



The view is here taken that the stellate or radially banded type of 

 vascular structure, such as is found in the Selago and Phleymaria sec- 

 tions of the genus, as also in the young plants and ultimate branches 

 and the roots of most of the species, is the primitive one for the genus. 

 The mixed L. cernuum type stands by itself, and has resulted perhaps 

 partly from the dominance of the leaf-tiee system over the cauline 

 vascular tissues in the very young plant, and partly from the fact 

 that along with the plagiotropic habit and the consequent fact of the 

 presence of the vascular cylinder in its full size and complexity in the 

 growing regions of the plant there is an irregular branching of the 

 cylinder (branching taking place from all four sides of the growing 

 apex), and hence a continual tendency to an indiscriminating mixing 

 of its tissues. In the type which is characterized by the parallel 

 arrangement of the vascular tissues we may recognize a modification of 



