in Rhodymeniales : //. Delesseriaccae . 193 
The procarps are scattered along the margin of the thallus. 
Fig. 25 represents a procarp in surface-view ; its similarity to 
that of D. sinuosa , as shown in Fig. 29, will be apparent at 
once. Fig. 24 represents a section through the thallus at a 
point where the pair of procarps arises. 
In the later stages the sterile cells derived from the peri- 
central form a compact group similar to that shown in Fig. 27. 
Nitophyllum Hilliae, Grev. 
Nitophyllum Hilliae is the largest and firmest of all the 
British species of Nitophyllum . The thallus is for the most 
part more than one cell thick. Like N. laceratum , it has the 
obscure venation of Ktitzing’s genus Cryptopleura. I am 
indebted to Mr. A. H. Church for fine specimens of this plant 
from Plymouth. 
The procarps are scattered over the thallus as in N. lace- 
ratum and D. sinuosa. On closer examination they differ in 
one important particular from both these species. While 
each pericentral cell in D. sinuosa and N. laceratum gives 
rise to a single carpogonial branch, in N. Hilliae I have found 
that each pericentral cell very regularly gives rise to two 
such branches. These curve in a crescent on opposite sides 
of the pericentral cell, and the trichogynes emerge on opposite 
declivities of the papillar elevation which marks the position 
of the procarps. As two carpogonial branches emerge on 
each surface, the swelling marks the site of four carpogonial 
branches. In this respect N. Hilliae is alone among the 
Delesseriaceae here described, though isolated instances of 
the same phenomenon occur in D. ruscifolia. 
In the genus Ceramium two carpogonial branches also 
arise regularly from one cell. 
Fig. 26 represents a surface view of a pair of carpogonial 
branches. Fig. 27 represents an early stage of a cystocarp. 
The group of pyriform sterile cells, which belong to two 
filaments, have already been referred to. The auxiliary cell 
has been formed, but has not yet given rise to gonimoblast- 
