HoLLOWAY. — Studies in the New Zealand Species of Lycopodium. 293 



walled parenchyma right up to the vascular cylinder. The metaxylera 

 elements in the central cylinder are more irregularly disposed even than 

 in L. laterale and L. Drummondii. Possibly it is more noticeable in 

 the present species simply because of the much larger size of its cylinder. 

 The pi'otoxylem is extended peripherally, this being especially marked 

 in the smaller stems and branches. In the main rows and groups of 

 phloem the centrally placed elements are large, and have the appearance 

 of sieve tubes, while those which surround them are smaller. There is 

 no rearrangement of the vascular tissues preparatory to branching, but 

 the main cylinder simply constricts into two more or less equal parts. 

 As noted above in the last species, behind the apex of a main stem or 

 large branch the differentiation of the metaxylem proceeds regularly 

 from the protoxylem inwards; in these regions also the larger-sized 

 phloem elements are seen to be empty, whilst the smaller phloem elements 

 which surround them have abundant darkly staining contents. There 

 is no definite radial arrangement of the vascular tissues in the ultimate 

 branchlets or the cones. 



L. densum. 



The single " seedling " plant found, which was branched in its upper 

 region, showed a radial arrangement in its vascular C3dinder, there 

 being six protoxylem groups connected in the centre by metaxylem and 

 alternating around the periphery with six groups of phloem. Both the 

 first root and the first adventitions root showed a triarch structure, the 

 phloem in both cases extending between the groups of xylem and occupy- 

 ing the centre of the cylinder. The main rhizome of this species is 

 stout and firm, and its vascular cylinder is among the largest in modern 

 Lycopodiums (fig. 91). The cortical tissues are throughout more or 

 less sclerenchymatous, and increasingly so towards the centre. The 

 middle region of the cortex is stored with starch. The xylem and phloem 

 are arranged in alternate bands or plates, which lie parallel to one 

 another in the plane of the ground. On the ventral side of the cylinder, 

 however, this parallel arrangement is disturbed by the giving-off of 

 adventitious roots. The division of the cylinder at a branching takes 

 place right and left of a line at right angles to the plates of tissue. 

 The number of groups of protoxylem is large, in the case figured there 

 being seventeen, while at the base of some of the larger aerial branches 

 the number may be as great as twenty-one. The xylem is differentiated 

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

 tubes and phloem parenchyma. There is a pericylic zone (^f cells three 

 or more in width. The aerial branches arise right and left of the 

 rhizome, and then immediately turn upwards and grow erect. At their 

 base the parallel structure is generally to be found, but this passes into 

 the radial form higher up. In one strongly growing aerial stem, at 

 a height of 4 ft. from the ground and below the first branching, 

 it was observed that there were as many as twenty-one protoxylem 

 groups, and that the configuration of the cylinder Avas markedly radial. 

 Immediately behind the growing apex of the main rhizome the central 

 cylinder is of the full size, and the differentiation of the metaxylem 

 takes place from the protoxylem inwards. In the ultimate branchlets 

 the number of orthostichies of leaves varies from six to eight, and the 

 protoxylem is in three or four massive groups. A common condition 

 is where the leaves are in six orthostichies in alternate whorls of three, 

 and there are three groups of protoxylem. However, it cannot be said 



