472 Fritsch . — The Structure and Development of 
wall at one point, as in the last-named species. But after the 
complete emergence of the zoospore it evidently sprang back 
into its original position (Fig. 25, f and /), and it requires 
careful observation of the empty mother-cell to make out the 
line along which the wall gave way for the emission of the 
contents. In other cases, however, the lid, just as in Oed. 
capillare , was cast off as a whole. 
I found considerable variation in the form of the root-ends 
in Oed . capillare. The normal type of attaching-disc (Haft- 
scheibe) is figured in Fig. 25, n ; it is no easy matter to 
reproduce its delicate divisions in a drawing. A sack-shaped 
basal end (as in Fig. 25, b) was not at all rarely observed ; it 
was found in individuals lying freely in the water (cf. next 
paragraph) and under rather abnormal conditions, large 
numbers of bacteria having formed in the cultures. Not in- 
frequently I found this sack-shaped root-end growing out into 
three or more rhizoids (Fig. 25, c ), which, as it were, were 
searching for a substratum. Probably this is always the result 
of further development of the type of base shown in Fig. 25, b, 
unless the cell dies off soon (as in the case figured) or empties 
its contents as a zoospore. 
Such a sack-shaped basal termination, which not infrequently 
is almost spherical, occurs as a rule and under normal conditions 
in Oed. cardiacttm 1 (Fig. 26, c\ This species forms an attaching- 
disc very like that of Oed. capillare (cf. Fig. 27, a), provided 
the zoospore attains a definite substratum before coming to 
rest. Otherwise the sack-shaped root-end is formed, never an 
elongated rhizoid as in the species discussed above. These 
basal portions are generally only slightly dilated, and in nearly 
every case grow out into a number of rhizoids, which can 
extend for a considerable distance and are not rarely successful 
in reaching a definite footing (Figs. 25, m and 27, k) ; in such 
plants with well - developed rhizoids, the original almost- 
spherical shape of the basal end is often hard to recognize 1 2 . 
1 Growing on leaves of Vallisneria spiralis in the chief tank of the water-lily house. 
2 In a few cases a transverse wall was observed cutting off this basal part as a 
special root-cell from the part above. 
