On THE PITHOPHORACEA. 5 
on each side of the oblique cell-wall which has, in the germination of the 
mother spore, sg, first divided this spore into two cells. These two 
parts of the thallus have, from the beginning, developed from the two 
opposite ends of the spore, and have afterwards also taken their growth 
in two opposite directions. *) One of these parts is a great deal better 
developed than the other and almost always branched, and moreover, it 
is this part which, as a rule, brings forth the spores. The other part, 
on the figures indicated by the letters rh, is always much more feebly 
developed (most frequently it consists of only one cell) and normally it 
develops neither branches nor spores. The former of these parts, which 
resembles the stem in the higher plants by bringing forth the organs 
of propagation and by growing upwards, I have, on these grounds, 
named the cauloid part of the thallus, or, in short, the cauloid (from 
zavids = stem, and eidos = form); and the latter, which shows a certain 
analogy to the root of the higher plants, by growing in an opposite 
direction to the stem and by being, as a rule, devoid of spores, the 
rhizoid part of the thallus, the rhizoid (from ¢éta@ = root, and éidoc = 
fOr). y 
However great the differences are, you may find a peculiar resem- 
blance between the taproot of the Dicotyledons and the Archisperme (Gym- 
nosperme R. Br.) on one side, and the rhizoid of the Pithophoracee on 
the other, in the fact that both are developed immediately out of the 
germ of the new plant (with the former the embryo, with the latter the 
spore), and in the circumstance, that they both form a direct continuation 
downwards of the primary axis of the stem system (in Pithophoracee of 
the cauloid). In the same manner as in P. kewensis nob. such a di- 
stinction between the cauloid and the rhizoid part of the thallus. is, as a 
tule, possible with all the other species of Pithophoracee that I have 
examined (pl. 4, fig. 1 and 15—19). 
In the comparison above drawn, only the morphological characters 
have, as may be seen, been taken into consideration. Regarding the rhi- 
zoid part in particular, it does not at all correspond physiologically 
with the root of the higher plants, because it is neither in a special 
) Regarding this, see more in extenso in the paragraph treating »the Germi- 
nation and Increase». 
2) This distinction of two morphologically different parts of the thallus, i. e. 
one cauloid and one rhizoid part, may be made also in a great deal of other Thal- 
lophytz, though these two parts are seldom so clearly separated as in Pithophoracee. 
