298 Transactions. 



early, even in plants which are still attached to their prothalli. In 

 figs. 100 and 101 are shown two such young plants. It will be seen 

 that, in marked contradistinction to what is found in the young plants 

 of L. voluhile, there are no gradual stages in the development of the 

 heterophylly to be traced in these young plants, but the transition is 

 sudden. In figs. 102g. and 102& are shown the dorsal and ventral sides 

 respectively of an ultimate branchlet in the mature plant of L. scariosum. 

 The vascular cylinder of the mature rhizome is very large. The number 

 of protoxylem groups varies from eighteen to twenty-seven, in the case 

 figured (fig. 96) there being twenty-three. The xylem and phloem are 

 markedly disposed in parallel plates. The sylem bands show an absence 

 of xylem parenchyma, and the xylem vessels are much smaller than in 

 most of the other species described. In each phloem band the row of 

 large sieve tubes is bounded on either side by phloem parenchyma, with 

 abundant cell-contents. The entire cortex is more or less sclereji- 

 chymatous. In the ultimate branchlets, where the heterophylly is most 

 marked, the configuration of the vascular cylinder is radial and 

 quadrarch. In the cones the leaves are in eight orthostichies in alter- 

 nate whorls of four, and the vascular cylinder is constantly hexarch. 



Summary . 



From the comparative study of the gross anatomy of the stem, roots, 

 and branches of the eleven New Zealand species of Lycopodium the 

 following leading facts stand out : In the most simple form, in the 

 " seedling " stem and in the first root and all young rootlets, there is 

 a single crescentic group of protoxylem embracing a single group of 

 protophloem. In slightly older plants the vascular cylinder both of the 

 stem and of the first adventitious root is either diarch or triarch, as it 

 is also in most rootlets in the adult plant, and the number of protoxylem 

 groups increases by splitting, so that a quardrarch or pentaixh radial 

 stage is attained. This is also the normal condition of the vascular 

 cylinder in the idtimate branchlets and in the cones of the adult plant, 

 except in L. cernuum and certain other allied species, in which the 

 arrangement of the vascular elements is indefinite and mixed through- 

 out the plant. In the! ultimate branchlets the radial condition has 

 resulted from the reduction in size of the mature vascular cylinder by 

 sueessive branchings. The leaf-arrangement on the ultimate branchlets 

 exercises no influence upon the configuration of the vascular cylinder 

 in those parts, the number of protoxylem groups in the latter being 

 dependent simply upon the order of the branch. In the main stems and 

 branches and in the large adventitious roots the configuration of the 

 central cylinder is stellate. The bands and groups of xylem and of 

 phloem in the central region of the cylinder are more or less cross- 

 connected, so that the actual centre may be occupied by a band or group 

 either of phloem or of xylem, but at the periphery the disposition of 

 both xylem and phloem is more or less ray-like. This form of vascular 

 cylinder is found in species which belong to Pritzel's Selago and Phlcg- 

 maria sections of the genus. There are certain important modifications 

 of this arrangement which are to be noted. In the first place, in 

 certain species belonging to the sections Innndata and Ctrniia — viz., 

 L. cernuum, L. laterale, and L. Drnmmondii — the protoxylem groups are 

 very much extended peripherally, so that the vascular cylinder is more 

 or less enclosed in a thin shell of protoxylem. This has also been 

 described by Boodle (1) in the case of L. salakense. Moreover, the dis- 



