288 EVOLUTION OF PLANTS 
Confervacee, Siphonex, and Phzophycez,— so that the 
possession of sexual cells showing a similar grade of 
development does not by any means necessarily imply 
relationship. 
The origin of the Pheophyceex, or brown alge, from 
free-swimming brown flagellate organisms, is by no 
means unlikely, and if this is shown to be the case, they 
must be considered as a line of development parallel 
with the Chlorophycexe rather than an offshoot from 
these. It may also be said of the red alge, that they 
may possibly constitute an entirely independent devel- 
opmental line, but this is less likely than in the case 
of the Phzophycee. 
The relationships of the Fungi is still an open ques- 
tion. Certain forms, the Phycomycetes or alga-fungi, 
especially the water-moulds and their allies, so closely 
resemble such siphoneous alge as Vaucheria, both in 
the structure of the thallus and in the character of the 
reproductive cells, as to leave little doubt of their 
probable derivation from some such green ancestral 
forms. These Phycomycetes may be said to bear 
much the same relation to these green alge that such 
parasites and saprophytes as the dodder and Indian 
pipe do to their green relatives among flowering plants. 
The question of the relation of the true Fungi, or 
Mycomycetes, to these alga-fungi, is by no means so 
clear, although it is generally supposed that they have 
been derived from some such forms. Some authorities 
claim, however, that the two groups are quite inde- 
pendent of each other, and that the line of Mycomycetes 
has originated from chlorophyll-less plants of extremely 
simple structure. 
