296 



Transactions. 



is stellate (fig. 93), and there are about a dozen groups of protoxylem. 

 As in the main stem, the whole of the cortex here also in sclerenchy- 

 matous. Branching of the adventitious roots and also of the lateral 

 rootlets is by dichotomy, and not infrequentl}' by a more or less exact 

 trichotomy. As noted above for the last sj^ecies, the smallest rootlets 



102 



Figs. 



99a, 996. — Lycopodium volubile. Portion of distichous region of ultimate branch 

 of mature plant, from dorsal and ventral sides respectively. X 4. 

 Figs. 102a, 1026. — Lycopodium scariosum. Portion of distichous region of ultimate 

 branch of mature plant, from dorsal and ventral sides respectively, x 4. 



show a single small crescentic group of protoxylem, while others show 

 two or three xylem groups. In the ultimate branchlets there is no 

 correspondence between the distichous habit and the number of proto- 



of the plant is 



xylem groups; the vascular cylinder in these 

 generally pentarch. 



regions 



L. ramulosum. 



In the stem of the young plant the xylem elements are more definitely 

 coherent than in the case of Jj. cernuum, but the disposition of the xylem 

 groups varies greath*. Both the cortex and the vascular cylinder of the 

 more deeply buried scaleless stems of this species are larger than those of 

 the scaly less deeply buried stems from which the aerial branches arise. 

 In both the middle region of the cortex is sclerenchymatous, and in the 

 more deeply growing stems the inner cortical zone is stored with starch. 

 In fig. 94 is shown the vascular cylinder of the smaller scaly rhizome. 

 In the larger rhizomes the number of protoxylem groups is generally eight 

 or nine. The elements of the xylem are arranged in rows and groups, 

 and do not show any tendency to separate from one another. There is 

 no differentiation either of the phloem into sieve tubes and phloem 

 parenchyma or of the xylem into vessels and xylem parenchyma. In the 

 cones the sporophylls are arranged either in four orthostichies in alter- 

 nate whorls of two or in six orthostichies in alternate whorls of three. 

 There are four groups of protoxylem in the central cylinder of the 

 cones, the groups being so broad and extended as to form the four sides 

 of an almost complete square. The metaxylem elements, however, vary 

 greatly in their arrangement. 



