Hollo WAT. — Studies in the New Zealand Species of Lycopodiuni. 297 



L. fastigiatum. 



In the stems of the youngest prothallial plants examined there were 

 two groups of protoxylem connected across by one or two elements of 

 metaxylem, and a group of protophloem on either side of this median 

 plate. In slightly older plantlets the number of groups of protoxylem 

 is three or four, and they are joined together at the centre by the 

 metaxylem elements. It frequently happens, however, that one or two 

 of these protoxylem groups become isolated, and then two groups of the 

 phloem become joined to form a band across the centre of the cylinder. 

 In the full-grown rhizome the cortex is mai'kedly differentiated into 

 zones. There is an outer narrow zone of very slightly sclerenchymatous 

 cells, which is separated from the inner main cortex by a narrow layer 

 of very large thin-walled parenchymatous cells. The inner main cortical 

 zone is strongly sclerenchymatous towards the centre. The vascular 

 cylinder is large, there being from fifteen to eighteen groups of proto- 

 xylem (fig. 96). The xylem and phloem are disposed in parallel plates. 

 This parallel arrangement, as in the other plagiotropic species which show 

 it, is disturbed on the ventral side of the cylinder, probably in relation to 

 the o-iving-off of adventitious roots. The xvlem bands are differentiated 

 into vessels and xylem parenchyma, and the phloem bands into sieve 

 tubes and phloem parenchyma, the latter having abundant cell-contents. 

 The pericyclic zone in this sj^ecies is very broad, and is differentiated 

 into an outer layer, three or four cells in width, whose cells are empty, 

 and an inner layer, five or six cells in width, staining brown with 

 safranin, whose cells show abundant contents. The arrangement of 

 leaves on the cones is constantly in eight orthostichies in alternate 

 whorls of four. The vascular cylinder of the cones also seems to have 

 a very constant configuration, consisting of five groups of protoxylem 

 joined together in a stellate manner, the centre of the cylinder being 

 occupied commonly by an island of phloem. 



L, scariosum. 



In the young prothallial plants of this species the vascular cylinder 

 is much stouter than in either of the last two species. The very 

 smallest and youngest stems sectioned showed never less than three 

 protoxylem groups, while both four and five gi'oups are commonly found 

 in the stems of young prothallial plants. The groups of phloem also are 

 large, and the centre of the cylinder generally shows several large-sized 

 elements of undifferentiated metaxylem. A series of transverse sections 

 of a prothallus and young plant j^i'esented an opportunity for observing 

 the changing configuration of the vascular strand as it jDasses from the 

 stem into the first root in the neighbourhood of the foot. In this 

 instance the young stem above showed five protoxylem groups. These 

 groups in the region immediately above the foot joined up with one 

 another around the periphery of the cylinder and separated again, 

 regrouping themselves in a most irregular manner. One striking con- 

 figuration was that of a somewhat irregular but continuous semicircle 

 of protoxylem elements, on the periphery of the cylinder opposite to it 

 there being a single compact group, and in the centre three isolated 

 elements of protoxylem among the undifferentiated metaxylem elements. 

 In the sections median through the foot the protoxylem groups were 

 observed to be arranged in a triarch manner, but below it they adopted 

 the form of a Greek omega, the root evidently preparing to fork. The 

 characteristic heterophylly of this species .aakes its appearance ver}' 



