HoLLOWAT. — Studies in the New Zealand Species of Lycopodium. 195 



characters, the natural cUassification of the species must take all these 

 characters into consideration, weighing one against another, and can only- 

 become an accomplished thing when the full life-history of many more of 

 the more important species is known. This is, of course, true in a greater 

 or less degree of every genus and family of plants, but it is especially true 

 of the present one. 



The stelar and cortical anatomy is very consistent in structure as it 

 occurs in the case of each of the four New Zealand species, but certain 

 small distinguishing features are worth recording. The text-figures illus- 

 trating the vascular structure of the four species show in each case the 

 ends of two bands of both xylem and phloem with the protoxylem and 

 protophloem groups, and also the adjacent pericyclic and cortical regions. 

 As in the case of the other New Zealand species, semi-diagrammatic drawings 

 of the complete stele have been 

 given in another paper (16). In 

 the stem of L. voluhile (fig. 13) 

 a very characteristic feature is 

 the exceedingly large size of 

 the sieve tubes. The chief meta- 

 xylem elements are also large, 

 and are noticeably flanked on 

 both sides of each band by small- 

 sized tracheides. The pericycle 

 is narrower than in the other 

 species. Practically the whole 

 of the cortex is strongly scleren- 

 chymatous. Three zones can 

 be recognized, however — an 

 inner narrow, exceedingly 

 strongly thickened zone, in 

 which the cells have been flat- 

 tened tangentially by mutual 



pressure and the cell-cavities almost obliterated ; a broad median zone of 

 circular, thick-walled cells, which passes into a narrow epidermal zone of 

 thin-walled cells showing air-spaces and bounded externally by a strongly 

 cuticularized epidermis. The whole stem and the vascular cylinder is 

 much smaller in size than in the case of the other three species. The 

 main features thus given of the stem-anatomy of L. voluhile — viz., the 

 comparatively thin stem, the woody cortex designed rather to impart a 

 wiry quality to the stem than to act as a starch-storing tissue, and also 

 the large open vascular elements — can be put into connection with the 

 scrambling habit of the plant. In the large adventitious roots the con- 

 figuration of the stele is strikingly stellate (16, fig. 93). There is no 

 modification of the vascular tissues in the ultimate branchlets by the 

 heterophyllous habit. 



The rhizome of L. densum is from two to three times as thick as that 

 of L. voluhile, and the vascular cylinder is very large. The cortex functions 

 as a storing tissue. There is a somewhat narrow, strongly sclerenchy- 

 matous, inner cortical zone, while the rest of the cortex consists of much 

 less thickened circular cells containing abundant starch. In the aerial stems 

 the whole of the cortex is strongly sclerenchymatous. The same rhizomes 

 which show the presence of starch in the cortex show also the cells of the 

 phloem parenchyma to be practically empty, but immediately behind the 



Fig. 1.3. 



— Lycopodium volubile. Transverse 

 section of portion of stele of main 

 stem. X 137. 



