36 Veit Brecuer WIrtrRock. 
of the thallus is, in short, so great that it sometimes meets with no small diffi- 
culty to identify, solely by the cauloid part, whether a sterile specimen 
belongs to a Cladophora or to a Pithophora (on the distinguishing char- 
acters in this case, see parag. 1, pag. 4). What gives sure distinctions, 
even if only the vegetative organs are taken into consideration, is, on 
the contrary, the nature of the rhizoid system. In Pithophoracee this 
consists, as a rule, of only one cell, viz. the one developed, immediately 
at the germination of the hypnospore, in a direction diametrically oppo- 
site to that of the cauloid. This rhizoid cell (which has, as we know, 
nothing to do with the attaching of the thallus) we regard, from reasons 
mentioned page 5, as analogous, in some degree at least, with the tap-root 
of the Dicotyledonew. But in Cladophoree (particularly in Cladophora fracta 
(Dillw.) Kiitz., which in other respects belongs to the most Pithophora-like 
species) the spore — which is here a zoospore — sends forth downwards, 
in germinating, one or generally several irregularly formed processes, 
serving as attaching organs, rhizines, which have nothing in common 
with the tap-root, but show a certain analogy to the adventitious roots 
developed in the germination of the Monocotyledonee. As no formation 
of parting-walls takes place between these rhizines and the germinated 
spore, they will consist merely of processes belonging to the lowest 
one of the cauloid cells, not of independent cells. In a great many 
Cladophoree, however, these rhizines are not the only constituent parts 
of the rhizoid system.*) <A plentiful development of pluricellular rhizines, 
comparable to the adventitious roots from the stem of the higher plants, 
takes place in the cauloid, especially in the genera of Agagropila Kitz. 
and Spongomorpha Kitz. These rhizoid organs are recognized as such 
by the circumstance that they are developed, in contrast to the cauloid 
branches, from the lowest part of their mother cells; that they increase 
downwards; that they contain but little chlorophyll; and that they serve 
as real attaching organs, which rather often have the end of the lowest 
cell transformed into a peculiar grasping organ, sometimes resembling a 
helicoid (see Ktrz. Tab. Phyc., part 4, pl. 83 Spongomorpha lanosa fig. g 
pestina which gives reason to suppose that helicoids of the same nature occur also in 
this form of Avgagropila. Besides these unicellular attaching organs, perfectly resem- 
bling those of the Pithophora-helicoids, pluricellular helicoids with a top rolled like 
a spiral or bent like a claw are fuund in numerous Cladophoree belonging to the 
genus Spongomorpha Kiitz.; see Kirz. |. ¢. pl. 75—78. 
') I am not quite certain whether all Cladophoree have other rhizines be- 
sides those developed from the germinated spore. 
