and H elminthostachys zeylanica. 37 
a thicker or thinner lining to the wall. Small nuclei are 
present in the protoplasm either distributed or aggregated 
together. The cells, in which these structures lie, are healthy ; 
starch is as a rule, though not always, absent from them. It 
is abundantly present in the adjoining cells, from which the 
Fungus is absent (Fig. 48), and in smaller grains in those of 
the superficial layers. 
In prothalli, only slightly larger than the one on which the 
above description is based, a remarkable change has come 
over the whole of the endophytic Fungus. Instead of healthy 
hyphae and vesicles there is found in each of the fungus- 
containing cells a number of small shrivelled bodies, which 
can sometimes be seen to be attached together by fine hyphae 
(Fig. 49). It is thus clear that the existence of the endophyte 
is arrested long before the growth of the prothallus is com- 
pleted. The materials for this are present in the form of 
starch, the distribution of which has been noted above. The 
starch can be traced up to the apex, but is absent from the 
peripheral tissue between the mature and old antheridia. 
By comparing older male prothalli the gradual withdrawal 
and utilization of this reserve starch can be followed, the last 
traces of it being detected in the cells close to the apex. 
With this last condition the arrest of growth of the sexual 
region is correlated, and in such prothalli mature or emptied 
antheridia are present close to the apex, instead of the young 
ones which occupy this position in prothalli capable of further 
growth. 
It would thus appear that the relation between the pro- 
thallus and the mycorhizal Fungus is somewhat peculiar in 
H elminthostachys, in the sharp distinction between a stage, in 
which organic substance is manufactured, and one in which it 
is utilized. During the former stage the Fungus is healthy, 
but the growth of the sexual region has barely commenced 
before the Fungus dies ; the further growth of the sexual 
region takes place at the expense of, and up to the limit per- 
mitted by, the amount of the reserve material. There is thus 
a definite limit to the full size of each male prothallus ; but 
