199 
Pellia epiphylla , (L.) Cor da, 
the thallus itself, where they measure from 5-7 /x in diameter. In the younger 
branches of the mycelium the finer, thin-walled type occurs again. These 
hyphae measure 1-4 1 u in diameter. The hyphae are very r.arely constricted 
in the thallus except in the region of the antheridium (see below). In only 
one case have constricted hyphae been observed in the thallu.s. 
In older plants heavily infected by the fungus, cells occur, dark brown 
in colour, in which the fungus produces curious structures somewhat 
resembling oogonia and antheridia. No further stages have been observed, 
however, and it is possible that they are merely indications of the hyper- 
trophy of the vegetative mycelium. 
In several cases the fungus has been observed in proximity to 
antheridia (Fig. 2). The fungus enters through the aperture of the 
Fig. 3. Longitudinal section through the thallus with archegonia, showing fungal hyphae 
in close proximity to them, x 125. h ., hyphae. 
cavity. No direct connexion has been observed so far between hyphae 
in the thallus and in the antheridium. The fungal hyphae in the 
latter are often constricted similarly to those in the rhizoids. When the 
antheridium is mature, and the antherozoids have escaped, the hyphae fill 
the empty antheridial cavity. 
Fungal hyphae, similar to those around the antheridia, have also been 
observed near unfertilized archegonia (Fig. 3). 
B. In the Sporophyte. 
The fact that the fungus was present in the sporophyte was not 
observed for some considerable time. Normal healthy sporophytes were 
repeatedly examined, and no sign of the fungus was discovered in foot, seta, 
or capsule. 
However, while the setae of the healthy sporophytes were elongating 
and the capsules dehiscing it was noticed that on other plants, much 
discoloured owing to extreme infection by the fungus, capsules were present 
Q 
