Fritsch, Observations on the young plants of Stigeoclonium Kütz. 371 
In the following pages I shall first discuss the ordinary type of 
young plant, then the specially modified epiphytic type and finally 
certain endophytic forms. 
2. The ordinary type of young plant. 
If any species of Stigeoclonium is retained in culture for some 
days, zoospores are formed and in a short time large numbers of 
young plants are to be found attached to every available object 
present in the water. Lacking that a number of zoospores frequently 
form a radial group, floating freely in the water, as is often the 
case in Oedogonium (cp. Fritsch 02®, p. 474); the young plants 
developed from these zoospores however rarely succeed in passing 
the 3- or 4-celled stage. 
The zoospore on coming to rest generally assumes an elongated 
elliptical shape, pointed and colourless at both ends (cp. Tab. XI, 
fig. 22; also Wille 90, p. 87, fig. 52D) and in this state often 
shows some resemblance to certain species of Characıum. The mode, 
in which this develops further, depends on the species, — especially 
upon the degree of branching and the extent to which the hairs are 
developed. Species, which have well-developed hairs, usually begin 
to form them very early; as an example I will describe the ger- 
mination of the zoospores in an undetermined species from a tank 
in the Herbaceous Department at Kew. The elongated, unicellular 
structure, formed by the zoospore on coming: to rest, commences to 
put out & colourless protuberance at the end opposite to that, at 
which it is attached. This protuberance rapidiy lengthens and 
becomes segmented, so as to form a long multicellular hair. Soon 
after the commencement of the formation of the hair, the chloro- 
phyll-containing portion of the cell beneath the just-described pro- 
tuberance becomes two-celled by the formation of a transverse wall. 
In this species branching took place at an early stage; the young 
upright filament then consisted of about three lower cells, filled with 
dense chlorophyll, the two succeeding ones had sparing contents and 
led off into the absolutely colourless cells of the hair-tip, the whole 
young plant consisting of about nine cells. The lowest cell first 
showed signs of branching, putting out a lateral process, which 
rapidly increased in size. When this had become distinct, the cell 
next above began to form a branch, which was developed either on 
the same or on the opposite side. !) 
apex. In Sig. nanum (Dillw.) Ktz. on the other hand the cells were much 
broader, and usually somewhat barrel-shaped; their length was about twice 
their diameter. The filaments were very abundantly branched and ended 
bluntly, no hairs being developed. The third species had quite a special 
structure of its own andas it will be described fully in the third part of this 
paper, it is unnecessary to say more about it here. Stig. variabile was ob- 
tained from the Victoria Regia Tank, St. nanum from the pond, wliilst the 
third species was found growing on leaves of Vallisneria spiralis in the middle 
tank ot the water-lily house. 
i) cp. the figures of this species, given in Annals of Botany. Vol. XVI. 
1902. p. 411. Fig. 22, 3 and 4. ıthink it very probable that these young 
plants belong to Stıg.tenue Rabh. The red cells, described on p. 410—412 
and ee in Fig. 22, 3 are undoubtedly due to the action of a member or 
the Chytridiaceae, as also are the red cells in the Aphanochaete, referred. 
to at the same place. 
