238 
F. E. Fritsch. 
pletely wanting, the upright filaments being attached merely by the 
basal cell, strengthened by the outgrowth of rhizoids from some of 
the lower cells of the upright axes. The radial upright system 
exhibits a sharp differentiation into long and short branches. The 
former consist of large, slightly barrel-shaped cells, with a small 
chloroplast forming an equatorial girdle in the otherwise colourless 
cell. The short branches arise in dense, often more or less whorled 
tufts, are richly branched, and consist of short cells, each occupied 
by a large chloroplast; the different branches terminate in more or 
less marked hairs. It is plain that the short lateral branch-systems 
are the seat of the main assimiiatory activity, and the production 
of swarmers and other reproductive cells appears to be confined to 
them. The large-celled long axes are probably in the main sup¬ 
porting and possibly also serve for purposes of storage. The 
differentiation of this Alga into main axes and lateral assimiiatory 
and reproductive appendages is most marked. 
In contrast to Draparnaldia, with its elaborate upright system, 
a large number of Chaetophorales exhibit more or less complete 
reduction of the erect portion, whilst the dorsiventral creeping 
base remains highly developed. In some (e.g., Gongrosira ) there is 
still a considerable development of upright branches, although 
these are short and commonly combine with the densely branched 
pseudoparenchymatous base to form a convex cushion. In others, 
the upright system is represented only by hairs (e.g., Aphanochcctc , 
Fig. 1 c, Ochlochcete , Ectochczte). Lastly, there are forms in which 
the upright portion of the thallus is completely suppressed, the 
whole consisting merely of the creeping base (e.g., Protoderma, 
Fig. 1 d, Pringsheimia). It should be pointed out that, in referring 
to these forms in this order, no probable line of evolution whatso¬ 
ever is implied; in fact, it seems likely that there are several 
distinct series of reduction of the upright system in the Chaetopho¬ 
rales. The instances are merely given as examples of varying 
morphological differentiation. 
Among the terrestrial Trentepohliaceae we encounter similar 
features. The genus Trentepohlia (Chroolepns) has a thallus differ¬ 
entiated into creeping base and upright threads (Fig. 1,^), the two 
varying somewhat in relative development in the different species, 
whilst in Phycopeltis and Cephaleuros the upright system is much 
reduced. 
In all the more extreme prostrate forms the base shows a 
tendency to become pseudoparenchymatous, a feature well seen in 
