33 
and Helminthostachys zeylcmica. 
apex being directed upwards. Prothalli of different sizes 
were found, but the earlier stages of development were not 
seen. The smallest prothallus obtained is represented in 
Fig. 30. Fig. 31 represents a rather larger prothallus, which 
was however capable of further growth, while that in Fig. 30 
has almost attained its full size. Both of them show a more 
or less swollen lower region, which bears rhizoids and is of 
a brown colour. From this a cylindrical growth has arisen, 
at the apex of which the growing-point is to be found, the 
antheridia arising in acropetal succession behind the latter. 
The distinction into a lower portion bearing rhizoids and an 
upper on which the sexual organs are situated is most clearly 
seen in Fig. 31. It can be traced in all the prothalli, and 
since the endophytic Fungus is contained in the lower portion 
this will be spoken of as the vegetative region, and the longer 
or shorter cylindrical upper part as the sexual region. 
The relative development of the vegetative and sexual 
regions, and consequently the general form of the prothallus, 
differs according to whether the prothallus bears antheridia 
or archegonia. There is in fact an imperfect sexual differentia- 
tion analogous to that known in the gametophyte of some 
other homosporous Vascular Cryptogams. Certain prothalli 
produce antheridia only ; others, after a few antheridia have 
been produced, bear archegonia. The fact that the female 
prothalli nearly always bear a few antheridia first, makes 
it probable that, up to a stage like that represented in 
Fig. 31, there would be little or no difference between the 
two forms. 
Three male prothalli are represented in Figs. 32-34. In 
them the vegetative region is relatively small. It is slightly 
lobed in the prothallus represented in Fig. 32, more strongly 
in the other two. This lobing of the basal region is not 
a true branching, but results from unequal growth of the 
originally unlobed basal region. A true branching, referable 
to the growing-point, has in no instance been observed, and 
may safely be regarded as exceptional. The sexual region 
is cylindrical, of fairly uniform thickness, and attains a con- 
D 
