538 
The nemathecia are borne on the short stipe of peltate leaflets dispersed on 
the surface of the frond of separate asexual plants. They are flat broad bodies that 
cover a great part of the stipe, in a number of two or more. When several 
nemathecia are present, they may meet and jointly cover a great part of the surface 
of the stipe. The structure of the nemathecia has been well described and pictured 
by DARBISHIRE (1895, p. 28) who ascertained that the nemathecium is only connected 
with the supporting organ in the middle where it has arisen from the cortical tissue, 
while the basal layer of the nemathecium is for the rest appressed to the frond. 
The nemathecia increase at the margin by the formation of tangential walls. Two 
years before, SCHMITZ treated the nemathecia of this Alga in his paper on 
Actinococcus (1893, p. 399 et sequ.). DARBISHIRE’s statements are in many respects 
in good accordance with those of SCHMITZ but as to the basal layer the two authors 
disagree. While DarBIsHIRE describes this layer as consisting of one or two 
layers of cells and as distinct from the surface of the frond with which it is in 
contact, SCHMITZ found that the growing border of the nemathecium is separated 
from the surface of the supporting frond by a slit. At a certain distance from the 
margin, the basal layer appears in contact with the surface of the frond with which 
it becomes closely united, the cells of the basal layer giving off prolongations toward 
the superficial cells of the frond with which they are said to fuse, with the result 
that the slit entirely disappears, and finally almost all the superfieial frond-cells are 
united with one or more cells of the basal layer, and the arrangement of the cells 
of the latter becomes very irregular. This fusing process takes place, according to 
SCHMITZ, even at the insertion of very young nemathecia and the author concludes 
from this that the nemathecia of this and some related species are particular 
parasitical alge growing on the surface of the fronds of Phyllophora and fusing 
with the presumed host-plant through cell-fusions. SCHMITZ gave to the parasite 
the name of Calacolepis incrustans. If this interpretation were true, the parasite 
would only attack the asexual plants and these would then be devoid of tetra- 
sporangia. As this is very improbable, particularly convincing facts must be 
demanded for supporting such an interpretation. It must be regretted that SCHMITZ 
has given no drawings illustrating the fusing process. DARBISHIRE has not succeeded 
in observing it (1894, p. 369); he declares (1895, p. 28) that the nemathecium only 
is in connection with the stipe in the place where it has arisen from the cortical 
cells. In this place the cortical cells first divide and grow out, and the young 
nemathecium thus formed breaks forth from the cortex; he can not, therefore, accept 
the view of SCHMITZ. 
I, too, have not succeeded in observing the fusions recorded by Scuitz. In 
specimens collected in September the formation of the nemathecia is easily observed. 
In the youngest stages a small group of cells situated just within the surface are 
seen dividing and extending outwards, causing a vaulting and distending of the 
cuticle. This distending early involves a bursting of the cuticle, and the active cells 
protrude, surrounded by their thin special membranes (fig. 523 B, C). The bursting 
