On the Pithophorace,e. 



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. x ) 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 rA, 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 

 xavXdg = stem, and elSog = form); and the latter, which shows a certain 

 analogy to the root of the higher platits, 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 qC& = root, and dSog = 

 form). 2 ) 



However great the differences are, you may find a peculiar resem- 

 blance between the taproot of the Dicotyledons and the Archispermce (Gym- 

 nospermce R. Br.) on one side, and the rhizoid of the Pithophoracece 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 Pitlioplwraceoe of 

 the cauloid). In the same manner as in P. keioensis nob. such a di- 

 stinction between the cauloid and the rhizoid part of the thallus is, as a 

 rule, possible with all the other species of Pithophoracew that I have 

 examined (pi. 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- 

 lophytse, though these two parts are seldom so clearly separated as in Pithophoracece. 



