Holloway. — Protocorm of Lycopodium laterale. 75 



adventitiously from the stem, and do not pass through the tissues of the 

 protocorm. The protocormous rhizome of L. laterale is a persistent organ, 

 and may be recognized in plants 2 in. or even more in height. It may 

 be stated that the protophylls both on the protocorm proper and on the 

 rhizome are essentially similar in appearance and structure to the ordinary 

 vegetative leaves borne on the young stem-axis. In no case either in 

 L. laterale or in L. cemuum was any transition between them to be observed. 

 L. laterale grows on damp peaty ground and around the margins of 

 marshes. L. cemuum and Phylloglossum also occur in New Zealand in 

 the Auckland Province in much the same kind of habitat, though on higher 

 ground rather than in the hollows. During the greater part of the year 

 ground of this nature is continuously wet, and holds much water, but in the 

 summer months it is liable to be dried up. The view taken in this paper 

 is that the large development of the protocorm in L. laterale is an adaptation 

 to carry the young plant over the dry season. This would seem to be 

 indicated in the continued lateral development of protophylls with swollen 

 bases, and by the distinction so frequently to be observed between the 

 original protocorm and the protocormous rhizome. The fact that the 

 protocorm of L. cemuum also occasionally extends laterally as a rhizome 

 indicates that the Lycopod protocorm is a plastic organ, and that too 

 much stress must not be laid from a phylogenetic point of view upon the 

 fact of its normally large development in L. laterale. The writer desires 

 rather to emphasize the fact that a well-developed protocorm, which in 

 its first stage is of the same nature as that so well known in L. cemuum, 

 has been found also in L. laterale; that it is there correlated with a 

 prothallus of the cemuum type; and that L. laterale belongs to the same 

 subgenus Rhopalostachya as do the other members of the Lycopodiaceae 

 (with the possible exception of L. phlegmaria) in which a protocorm has been 

 recorded. 



Conclusions. 



1. In L. laterale and occasionally also in L. cemuum (though there to 

 a. less extent) the protocorm is capable of considerable development, and 

 constitutes the plant-body proper for a lengthy period. The vascular 

 strand of the stem and first root takes a course through its tissues. The 

 rhizome of L. laterale may even branch and give rise to more than one 

 stem-axis. 



2. There is a marked developmental distinction in L. laterale between 

 the original protocorm and its rhizomatous extension. This suggests that 

 the two portions must be interpreted apart from one another. 



3. In L. laterale the manner of development of the protocormous rhizome 

 suggests that its large size is an adaptation to carry the young plant over 

 the dry season which normally always follows the wet winter season. 



4. In L. laterale the protocorm is associated with the cemuum type 

 of prothallus, and this is the case also in the other Lycopodiaceae in which 

 a protocorm has been recorded. This type of prothallus has been stated 

 on other grounds to be primitive for the genus. The fact that these 

 protocormous species belong to two groups in the subgenus Rhopalostachya 

 suggests a certain degree of antiquity for the protocorm within the genus 

 Lycopodium ; and, assuming the primitive nature of the cemuum type 

 of prothallus, would also suggest that the subgenus Rhopalostachya com- 

 prises the more primitive members of the Lycopodiaceae, and that the genus 

 as a whole should be read as a reduction series rather than as a series which 

 has progressed from those forms which show the simpler type of sporophyte. 



