HoLLOWAY. — Studies in the New Zealand Species of Lycopodium. 289 



and L. ramulosuin are to he regarded simply as a special adaptation, 

 and would conclude that this lends weight to the theory that the Lycopod 

 protocorm in general may best be interpreted in this way. The fact that 

 the protocormous species are representative of three distinct sections of 

 the subgenus Ehopalostachya, in which there is a considerable variation 

 in the character both of the ganietophyte and of the mature sporophyte 

 generation, and is found also in the allied genus Fhylloglossum, is signi- 

 ficant, as indicating a considerable degree of antiquity for the protocorm 

 within the genus Lycopodium. 



V. Gross Anatomy op Stem and Branches. 

 L. Selago. 



" The vascular cylinder of the mature stem of this species in cross- 

 section is stellate in appearance (fig. 85). The xylem rows and protoxylem 

 groups are stout, the latter being extended around the periphery of the 

 cylinder in thick masses. At the base of the adult stem there are five 

 to seven such protoxylem groups. The configuration of the vascular 

 cylinder is variable: the centre may be occupied by xylem, or, as in the 

 figure given, by an isolated group of phloem. The cortex is differ- 

 entiated into three different zones; the innermost of these consists of 

 cells whose corners are lignified, the outermost is developed as a broad 

 zone of sclerenchymatous thick-walled tissue, and the middle cortex con- 

 sists of a loose tissue of large thin-walled parenchymatous cells, through 

 which several roots take their course. The vascular strand of the root 

 generally consists of a large crescentic group of xylem embracing a single 

 group of phioem; but in some roots there are two groups of xylem 

 separated by a band of phloem; while in others, again, besides the main 

 xylem groups there are a number of small isolated groups of protoxylem, 

 in these cases the phloem being also in more or less isolated patches. 

 A transverse section through the upper part of the stem shows the xylem 

 in six stout rows radiating from a common centre, the protoxylem 

 being in thick groups at their extremities. In this part of the stem 

 there is no development of sclerenchymatous tissue in the cortex. 



L. Billardieri. 



In all the prothallial plants of this species shown in figs. 7-12 the 

 vascular strand of the stem consisted of a single small crescentic group 

 of protoxylem, enclosing between the horns of thel crescent a single 

 gi-oup of protophloem. In the plant shown in fig. 11, which was about 

 1| in. in height, and possessed five leaves, the layer of cells immediately 

 surrounding the pericycle had become slightly sclerenchymatous. The 

 plant in fig. 12 showed two roots, each surrounded by a zone of well- 

 developed sclerenchyma two cells in width, traversing the cortical 

 tissues of the stem. The strand in these roots consisted of a single 

 crescentic group of protoxylem embracing a single group of protophloem. 

 By the time the young plant has developed a dozen leaves the stem 

 vascular cylinder shows two groups of protox3-lem, which have been 

 formed by the two horns of the crescent separating and the phloem 

 extending between them. At this stage also the outermost layer of cells 

 of the cortex has become slightly sclerenchymatous, as well as the 

 layer immediately surrounding the pericycle. As the plant develops, the 

 central cylinder becomes triarch by the splitting of one of the groups 

 of protoxylem into two, the three groups of protoxylem alternating with 

 three groups of phloem, the centre also being occupied by phloem. 



10— Trans. 



