360 CASPARY, ON THE ZOOSPORES OF CHROOLEPUS. 



which the zoospores are about to escape, a division of the 

 contents into small oval cells is clearly perceptible, (fig. 5), 

 and at the side, or near the top, the wall is extended into a 

 short papilla. (Figs. 5, 7, p.) The contents emerge in the 

 form of a well-defined vesicle, with the zoospores, penetrating 

 through the ruptured papilla (figs. 6, k, 8, k) ; sometimes, 

 however, no vesicle is formed. A few moments after emerg- 

 ing, the vesicle bursts, doubtless by absorption of water, and 

 the zoospores swim about in every direction. The remnants 

 of the vesicle are of a gelatinous nature. The escape of the 

 zoospores was observed from nine in the morning till four in 

 the afternoon, and seems to depend, not upon the influence 

 of light, but solely upon the effect of moistening with water. 

 The zoospores are very small, O0035 to 00033 mm. They 

 are filled with reddish-brown granular matter, the apex alone 

 being free and hyaline; there are two cilia, about three or 

 four times as long as the spore. The apex, with the cilia, 

 is directed forwards. They rotate perpetually whilst swim- 

 ming j their motion being so rapid as to prevent a clear view 

 of them, except when stopped by some obstacle, or when 

 their motion is becoming retarded. When killed by con- 

 centrated solution of iodine, or iodide of potash, the zoo- 

 spores appear brown, with the exception of the apex, which is 

 hyaline as before ; the cilia are very little browned, but be- 

 come more distinct. The cell is surrounded by a clear, 

 highly-refractive border (figs. 10, 11, 12), looking like gela- 

 tine, but which may be only an optical appearance. Treated 

 with iodine and diluted sulphuric acid, the whole zoospore, 

 apex and cilia, become deep brown. (Fig. 13.) After con- 

 tinuing in motion for about an hour, the zoospores become 

 sluggish, sink, become globular (fig. 15), elongate them- 

 selves (fig. 16, a, b, c), and shortly a division of the cell 

 takes place by a transverse septum. (Figs. 17, a, b, c, d.) 

 Some reddish-brown granules usually remain behind in the 

 empty mother-cell, and in the remnant of the vesicle. (Fig. 

 9, k.) Oftentimes some zoospores cannot emerge from the 

 mother-cell, and then they sometimes geminate in it. 



Chroolepus umbrinum, Kg. 



Chroolepus umbrinum, Kg. ' Pliycol. gener.,' 1842, p. 288. 4 Kaben- 

 liorst Deutscli. Krjptog.,' 1845, ii, 2, 87. 



This plant is common about Bonn, on the bark of trees, 

 in the form of a reddish- brown, scentless, thin stratum, prin- 

 cipally on the northern side of the tree. The zoospores were 



