in Rhodymeniales : II. Delesseriaceae. 183 
reacts on the pericentral cell, which is pushed back against 
the central cell, and thus lost sight of. This may possibly 
account for the statement that the pericentral cell gives rise 
to the carpospores. 
After the stage represented in Fig. 14, I have not been able 
to find any vestige of the carpogonial branch. It probably 
atrophies and disappears. The rest of the development of 
the cystocarp consists chiefly in the luxuriant branching 
of the gonimoblast-filaments, by which the sporogenous 
tissue attains considerable bulk in this species. The sterile 
derivatives of the pericentral cell are pushed off, and may 
often be seen lying at the peripheral part of the fertile tissue. 
In the mature condition the contents of the cystocarp exhibit 
a lobed appearance (Fig. 10), owing probably to the partial 
separation from one another of the products of a few main 
branches. Adventitious filaments seem to arise along the 
larger branches comparatively late in their development 
( F ‘g- J 5 )- 
The mature cystocarp-bearing branches are considerably 
longer than the procarp-bearing branches. This is probably 
due to a general elongation of the cells already formed rather 
than to continued apical growth. Wille (’ 87 ) has shown that 
in this species there arise from the internal cells of the thallus 
in the older parts numerous hypha-like cells whose function 
he considers to be storage. These arise in the basal parts of 
the cystocarpic branches, and to some extent may account for 
the greater length. 
Delesseria alata, Lamx. 
This plant presents several striking differences of habit from 
D. sanguined. While it possesses an equally well-marked 
midrib, the laminar portions are so reduced that the appear- 
ance is more that of a winged stem, which is the true 
morphological equivalence in both cases. In D. sanguinea , 
however, the proliferations of one season do not branch again 
O 
