210 Transactions. 



In the three New Zealand species dealt with above it is present at the actual 

 base of the prothallus, having entered probably very early in its develop- 

 ment. It occupies the whole of the tissues in the basal cone except at 

 the meristematic apex, being found even in the epidermal cells at the basal 

 point (figs. 1, 9). At first the fungus is in the form of hyphal coils which 

 are in actual connection with the mycelium in the outside soil by means of 

 hyphae which are to be found running through the rhizoids. As these 

 rhizoids die off from the older parts of the prothallus, each being cut off 

 at its base by a strongly thickened transverse wall, the fungus in these 

 older regions becomes isolated from that in the soil, and probably ceases 

 to function. The fungal coils soon disappear in many ,of the cells, their 

 place being taken by clusters of darkly-staining oval " spores " (fig. 10). 

 I do not know whether or not the fungus is at all used up by the growing 

 prothallus, but I should say not, as in even mature prothalli the cells in 

 the basal cone are still occupied either by the coils or by the " spores." 



A little forward from the basal cone the fungus has begun to penetrate 

 between the cells as well as occupying their cavities, so that the cells appear 

 loundish in section. It is especially jiresent in this intercellular position 

 at the centre of the prothallus, and produces its spores there also (fig. 12). 

 A little higher up the prothallial body the fungus becomes more localized, 

 avoiding the centra!" core of cells which has begun to function in the 

 translocation of food material. The cells of this fungal zone throughout 

 the vegetative portion of the main prothallial body preserve their ordinary 

 form and are in no way altered by the presence of the fungus. Their nuclei 

 also appear large and healthy, showing that the fungus has exercised no 

 harmful effect. I have not been able to distinguish in these prothalli the 

 multinucleate vesicles which have been described as occurring in the fungal 

 zone in the prothalli of the clavatum and complanatum types. All that are 

 here apparent are the dense hyphal coils and the clusters of spores. As 

 the prothallus grows, the fungus pushes forward, always occupying its 

 particular zone, except that at length when 'the sexual organs and para- 

 physes are initiated it is confined to the ventral side of the prothallus 

 body (fig. 14). In the forward, bulky, generative region the fungus is 

 altogether absent. Its most forward position is shown in (fig. 15), and it 

 wiU be observed that even here the coils have begun to be transformed 

 into the spores. 



The fungus is also present in the lateral branches, being confined there 

 also to a particular zone, avoiding the centrally-placed conducting-cells 

 and the epidermis. Here, too, it is intercellular as well as intracellular, 

 and the clusters of spores are a well-marked feature (figs. 20-22). The 

 distribution of the fungus in some of the long thin branches is discontinuous 

 (fig. 1), from which it would appear that fresh infection can take place 

 from without through the rhizoids (see also fig. 9). In those stouter 

 branches which have begun to form sexual organs and paraphyses the 

 fungus is only present along the opposite side of the branch (figs. 28-30), 

 the branches thus being bilateral. Sometimes it is to be noticed that when 

 a branch is beginning to swell at the apex preparatory to the formati^fn of 

 antheridia the fungus is thickly aggregated immediately behind this point, 

 there occupying the whole of the tissues of the branch (fig. 24). The 

 " resting " club-shaped branches are always very densely infected, there 

 being no long narrow central conducting-cells (figs. 1, 25, 26, 30). The 

 actual apex of the resting process is, of course, clear of the fungus, but 

 the latter reaches right up behind the apex, being found there as dense 



