PPE See ee LET B= CY hele oe Aa Te eee Pe eee ee Teele eee ae 
1893.] The Zoospores of Draparnaldia, 297 
As soon as the zoospore is free it darts rapidly away, with 
a rotary motion, and keeping the hyaline end forward. 
Under the microscope it never moves far in the same direc-. 
tion, but seems to tuzn at random. It is almost impossible 
to determine with any degree of accuracy the rate of their 
motion, but the result of repeated trials indicates an average 
velocity of about 6™ per minute. 
The period of activity does not seem to be very long—in 
no case observed longer than seven minutes. Judging from 
the distance to which they sometimes travel it must often be 
rather longer than this. At the end of the period the mo- 
tion diminishes in velocity, and the body begins to rotate 
around the hyaline end. This motion soon grows slower, and 
after a few final quivers it ceases. In settling down the zoo- 
spores show a tendency to collect in groups like that shown 
in figure 5, or to attach themselves by their hyaline ends to 
bits of gravel, the larger filaments of the plant, or in fact any 
object which comes in their way. One often sees old plants 
completely covered by the masses of zoospores fastened to 
“m. No signs of conjugation have been seen, but most of 
the Zoospores germinate freely. 
The contraction of the vacuoles ceases soon after the zoo- 
= ceases its motion, and the cilia disappear. The cell 
begins to elongate and a slight disc is formed on the 
vides Bours or may be delayed for several days. ie di- 
., pore in such a way that the pigment spot always 
“gare the basal cell i It oy eee till four or 
ae s have been formed (fig. 9), when it begins to grow 
cell be, and seems to be absorbed. About this time the basal 
Over “a to form an hyaline filament, which grows rapidiy 
plant, substratum, and serves as a hold-fast for the young 
ten time the filament has reached a length of ten oF 
whic <a Fis = has elongated into a multicellular bristle, 
the filamens © rapidly soon becomes several times as long as — 
tm Ht (figs. 10, 11). Of course the growth of the fila-— 
Peet be intercalary. From this point the young 
