598 Church . — The Structure of the Thallus of 
septa of the second order, owing to the fact that the game- 
tangia are not constant in position, do not necessarily possess 
an equal significance ; that is to say, a septum does not 
necessarily imply a point of ramification or even origin of 
a leaf when reproductive processes are concerned This again 
not only explains how it is that the special ‘ sporangial ’ 
outgrowths of Neomeris , for example, have been described as 
‘ terminal branches, 5 and lends support to the hypothesis 
put forward in explanation of Stage II, as also further 
suggesting that the septum used as a landmark by Solms- 
Laubach in A. mediterranea may be a special formation in 
connexion with the high degree of specialization of the cap as 
a reproductive organ ; but it leads on to the solution of the 
difficulty which seems to exist as to the real nature of the 
so-called c aplanospores.’ In these plants, it must be clearly 
understood, we are dealing not with cells, but with coenocytic 
masses of protoplasm. The special coenocytic masses which 
are entering on a reproductive phase, delimit themselves from 
the rest of the plant by a formation of membrane giving rise 
to a special gametangium, utilizing for the purpose at least 
some part of the original membrane of the vegetative thallus. 
This coenocytic mass in the majority of the recent genera 
undergoes further partition ; but the smaller coenocytic aggre- 
gates, instead of utilizing part of the membrane of the 
gametangium for their own investment, as in the segmenta- 
tion of cellular tissue, form complete new membranes 
individually, and thus effectually isolate themselves. The 
so-called ‘ aplanosporangium 5 therefore is to be regarded, 
not as a spore-producing organ, but as a multilocular game- 
tangium, of which the £ aplanospores 5 are the component 
loculi lying free inside the original membrane. The formation 
of solitary ‘ aplanospores, 5 as in N. dumetosa , represents, then, 
the retention of the latter mode of formation, only a single 
loculus being however developed, and points to a descent 
from a type in which numerous distinct loculi aplanospores 5 ) 
were developed. In the single £ aplanospore 5 therefore we 
have the highest type of gametangium attained in the Dasy- 
