594 Church. — The Structure of the Thatlus of 
elongated internodes and long wavy segments ; Chlorocladus 
with a terminal ‘ coma ’ recalls the later type of Stage I 
(Fig. 2) ; but on the other hand, while retaining a primitive 
type of thallus, all three of these genera have specialized their 
reproductive organs, and these arise as new outgrowths from 
the leaf, borne either laterally or in the angle of its ramification. 
In the latter case, owing to their contents being delimited by 
septa similar to those as the points of ramification of the leaf, 
they have often been described as leaf-segments. Dasycladus 
clavaeformis alone retains a definite gametanguim, the others 
attain to the so-called aplanosporangia. 
Exceptional cases of branching of the main axis to form 
two equal individuals, previously noted for Stages I and II of 
N. dumetosa , find a parallel in similar examples in Aceta- 
bularia mediterranean , Botryophora occidentalism , and they 
may also be observed in Dasycladus clavaeformis. 
The meaning of the delimitation of a special basal segment 
in Stage II, is at first sight not clear; it can scarcely be 
a mechanical necessity, nor can it be regarded as purely 
transitional to the cortex-formation of Stage III. The fact 
that the type is retained in a high state of perfection for 
as high an average number of whorls as is the case in Stage I 
or Stage III, may be taken perhaps as an indication of its 
importance at some period in the life-history of the group. 
Perhaps a reasonable working hypothesis is that we have 
here the first step in the specialization of the ‘leaf’ into 
assimilating and reproductive portions, and that the basal 
portion represents the primary gametangium for the Dasycla- 
daceae, with the exception of the three previously noticed 
Dasycladus types which have specialized their reproductive 
organs as new outgrowths on a thallus which is structurally 
in Stage I. There is no difficulty in conceiving such a Dasy- 
cladus type in which the protoplasm of the leaves, on reaching 
the reproductive stage, streamed down to the lower portion of 
the basal segments and there cut itself off by a septum ; after 
1 Woronin, Ann. Sci. Nat. 1862. 
2 Cramer, I. loc. cit., Taf. V, 21. 
