HoLLOWAY. — Six New Zealand Species of Lycopodiura. 359 



the vascular tissues of the stem later pass bodily. A longitudinal section 

 of the young plant at such a stage as that shown at Plate XXXI, fig. 2, shows 

 that the first root originates as an irregular extension of the tissues of the 

 protocorm. In the case of L. laterals, the first root arises very late, as a 

 superficial outgrowth of the protocormous " rhizome," at one of its ends 

 (Plate XXXI, fig. 7). As the vascular tissues of the stem develop they pass 

 down bodily into the rhizome, and, surrounded by a zone of sclerenchyma, 

 make their way through it immediately beneath its dorsal surface into the 

 root-like protuberance. A longitudinal section of the plant figured at 

 Plate XXXI, fig. 7, showed the tissues of the rhizome continuous with those 

 of the root. In each of the species L. Billardieri, L. volubile, and L. scariosum 

 prothallial plants were observed in which the first root had just made its 

 appearance as a conical outgrowth at the base of the stem, directed out- 

 wards and downwards (Plate XXXI, figs. 10, 17). In these species the root 

 is not differentiated till the apex of the stem has reached the surface of the 

 soil and assimilatory leaves have begun to develop. Longitudinal sections 

 of the young plants of L. volubile and L. Billardieri (figured at Plate 

 XXXI, figs. 10 and 17 respectively) showed that in each case the vascular 

 tissues of the stem passed directly down the root, and did not enter the 

 foot. 



The question of the origin of the first root is suggested by the study of 

 the development of the first root in L. cernuum and L. laterale. In his 

 book on " The Origin of a Land Flora " Bower says, " The origin of the 

 root may be held to have been accessory in evolution, as it is seen to be late 

 and variable in individual development." This view does seem to be in 

 accordance with what has been noted above. The idea suggests itself 

 from the study of L. cernuum and L. laterale that one way in which the 

 origin of the root may have come about was from the irregular growth and 

 branching of the protocorm. In both these species the protocorm, by 

 means of its rhizoids, acts as a root for a longer or shorter period ; and in 

 the case of L. laterale the protocorm grows irregularly to a considerable 

 extent, and may even branch. Also, in both species the early stages in the 

 development of the first root are in no way different from the further 

 irregular extension of the tissues of the protocorm in the form of a protuber- 

 ance. In the case of L. Billardieri, L. volubile, and L. scariosum the very 

 late appearance of the root is probably to be put in connection with the 

 increased dependence of the young plant upon its prothallus for food- 

 supplies. 



Protophylls. 



In both L. cernuum and L. laterale, before the stem axis, with its regular 

 leaf system, is differentiated, the work of assimilation is performed partly 

 by the protocorm (which is well provided with chlorophyll), but especially 

 by certain leafy extensions of the protocorm, to which the term " proto- 

 phylls " has been applied. These protophylls bear numerous stomata, and 

 in longitudinal section show a vascular strand leading down into the proto- 

 corm. They are few^ in number in the case of the young plant of L. cernuum, 

 not more than five or six being formed before the stem axis is differentiated 

 (Plate XXXI, figs. 2, 3) ; but in the young plants of L. laterale, where the 

 protocormous stage is a lengthy one, they are much more numerous. 



There is no sudden change in the passage from protophylls to stem 

 leaves ; in fact, in these two species the regular foliage leaves are not very 

 much different in form from the simpler protophylls. 



