368 



JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



3. Resting " sporangia " (dauersporen). Each gives rise to a 

 sporangium-sorus, which escapes as such from tlie parent cyst. 



The species grouped in the section Eusynchytriurn possess the first 

 and second of these types; the species within the sub-genus Pycno- 

 chytrium possess only the third. In Kryptogamenfiora der Mark 

 Brandenburg four species are recorded under the sub-genus Eusyn- 

 chytriurn; of these only Synchytriuni taraxaci has been fully inves- 

 tigated. The germination of the " dauersporen " of the remaining three 

 species has not been observed. Since two kinds of spore have been 

 described for Chrysophlyctis, a comparison may be made with the 

 Eusynchytria and with the only species which has been completely 

 described — S. taraxaci. Peecival* states, with regard to the ger- 

 mination of the "resting" sporangium of Chrysophlyctis : "In no 

 case was I fortunate enough to see the splitting of the sporangial wall 

 and the escape of the swarmers. The empty ruptured cases, however, 

 were frequently found in drops which had been left six to ten days, and 

 in some instances the inner sacs with their contents were observed 

 free from the outer thick walls, having apparently come out through 

 ■gaping slits in the latter." Now, in S. taraxaci it is stated that the 

 ' ' dauersporen ' ' give rise to zoospores direct ; the escape of a thin- 

 walled sac from the resting cyst is described only in the Pycnochytria. 



There remains, however, a still more important point, regarding 

 which the information is by no means definite. A prominent feature 

 in the genus Synchytrium is the formation of a sorus of sporangia 

 within the parent reproductive body. The number of sporangia 

 formed in each sorus is considerable — in S. aureum, 150 to 

 200; S. glohosimi, about 200; S. mercurialis , 80 to 9o or 120. Now 

 Pebcival states, with regard to Chrysophlyctis : " The parasite, how- 

 ever, produces another type of sporangium, chiefly during May or June. 

 These are thin transparent sacs, either produced singly or two to five 

 together, forming a sorus of sporangia enclosed within a brown coat, 

 which consists largely of the brown altered cell-walls of the host in 

 which the parasite has become encysted." It is not certain from 

 Percival's account that the sorus in Chrysophlyctis is developed 

 within the parent membrane, as in Synchytrium. He has advanced no 

 evidence to show that the formation of two or more sporangia is not 

 merely the result of the segmentation of the vegetative body — each 

 segment forming a separate free sporangium. No striking similaiity 

 with the sporangium-sorus of Synchytrium has been conclusively 

 demonstrated. Again, the number of sporangia produced is small (one 

 to five), and it is not clear whether the formation of a single sporangium 

 is the usual or an exceptional occurrence. 



With regard to the contents of the sporangia, Pebcival states that 

 the thick-walled sporocysts contain each several hundred zoospores, 

 and usually large numbers of oil globules of various sizes. Tlie 

 zoospoi-es found within such sporangia are often not of the same size, 

 but when found free-swimming in the water are oval or pear-shaped 



* I.e. p. 440. 



