On THE PITHOPHORACES. 33 
pointing somewhat upwards, which is separated, when it has attained a 
length which exceeds the diameter of the mother cell 2—5 times, from 
its mother cell by a parting-wall placed at the base of the process, and 
thus becomes an independent cell. This cell, the lowest one in each 
branch, is consequently formed by cell-prolification. In most cases, 
a longer or shorter series of cells is afterwards formed by this cell, 
exactly in the same manner as the cells of the principal filament by the 
first cauloid cell. In a couple of species, the system of ramification 
does not gain any further development (in. these, branches consequently 
exist only of the l:st degree), but in the other, branches of the 2:d 
degree are formed according to the same law as those of the l:st, and 
in two even branches of the 3:rd degree exist. Most of the cells, the 
top cells excepted, form branches (at least in the principal filament), 
this being done acropetally, thus, that the formation of branches begins 
in the lower and older cells, and proceeds to the upper and younger. In 
the manner now indicated is formed an Alga which is as to its cauloid 
Cladophora-like, 1. e. consisting of ramified series of cells. Its rhizoid 
consists, as has been mentioned above, generally of only one cell, 
growing in a direction opposite to that of the cauloid. This cell, which 
is analogous with the root system in the higher plants (especially with 
the tap-root of the Dicotyledonew) as to its morphological, but not its 
physiological character, does consequently not serve as an attaching organ of 
the thallus. The plant is most frequently not at all attached, and when it 
is (as happens now and then), it is with the assistance of peculiar tendril- 
like organs, developed from the cauloid and called, by me, helicoids. When 
the specimen has attained its full size, the formation of spores commences. 
It is effected in the following manner. The upper part, */,—'/, of theemother 
cell of the spore, is somewhat widened. ‘The chlorophyll-coloured proto- 
plasm in the lower, not widened part of the cell then passes, little by 
little, into the upper and widened part, till it is quite filled with chloro- 
phyll-coloured protoplasm. A transversal cell-wall is then little by little 
(succedaneously) formed, just below the point where the widened part 
of the cell commences. In this manner are formed one lower cell con- 
taining but little protoplasm, almost devoid of chlorophyll, the so-called 
subsporal cell, and one upper cell, rich in chlorophyll and reproductive, 
the spore. Its shape is as a rule cask-like or cylindrically cask-like. *) 
1) In some species of Pithophora the spores are rather often purely cylindrical. 
The spores of this shape are formed in the same manner as the cask-like, only with 
the difference that a widening of the upper part of the mother cell does not take place. 
Nova Acta Reg. Soc. Ups. Ser. III. 5 
