Edgbrley. — PPQthallia of Three Neic 'Zealand Lycopods. 



105 



more freely, several branches often arising side by side, which never occurs 

 in'a vegetative branch. (Figs. 24, 25, and 26.) 



|The branches may die off behind and form new prothallia. The same 

 would happen if a branch were accidentally detached. In some cases 

 prothallia are found surrounded by numerous detached branches, whose 



30 31 



Fig. 29. — Young sporophyte detached from prothallium but still showing foot. X 2. 

 Fie.s. 30, 31. — Prothallia of L. Bilkirdieri, bearing young sporophyte with first root 

 developed, r, root. X 2. 



rhizoids are interlaced with those of the parent prothallium. In this way 

 prothallia are able to increase rapidly when circumstances are favourable, 

 a power which is no doubt of great value, since the initial difficulty in the 

 germination of the spore is so great. 



Minute Structure of. Vegetative Brunches. 



A longitudinal section of a vegetative branch shows a certain differenti- 

 ation of tissues. A mature branch (fig. 32) shows, — 



(a.) In the centre several rows of elongated cells with scanty contents. 



\b.) Then two rows of cells, the region infected by the fungus. These 

 cells are equi-dimensional and contain a distinct nucleus. In many of 

 these cells the fungus hyphae form a dense skein, and in others there were 

 several bodies which stain very deeply with haemalum. Further search 

 showed that these dark bodies arose from the fungus, and are probably 

 spores. The fungus was also intercellular. 



(c.) A single row of elongated cells. 



(d.) The peripheral layer, usually a single row of cells, elongated 

 parallel to the axis of the branch, and covered with a thin cuticle. At 

 intervals are cells rather shorter, which give rise to rhizoids. These cells 

 are the only ones of the peripheral layer to contain fungus filaments. 

 A branch treated with caustic potash and stained with iodine showed the 

 presence of numerous pits on the cell- walls lying between any two of the 

 cells of the peripheral layer. The external wall and the wall opposite 

 to it were not pitted. Careful search failed to reveal similar pits in the 

 transverse walls of the central tissue which Treub describes as present, 

 in L. phlegmaria. 



Growing-point. 



A longitudinal section of the growing end of a branch revealed the 

 presence of two initial cells (fig. 33) which are characterized by large 



