CHYTRI 1)1 ALES 



81 



We are ignorant of the life cycles of a considerable number 

 of species but apparently the majority belong to Pijcnochyirium. 

 De Bary gave this group generic rank and Schroter (1892: 73) 

 follows the same procedure. In the present incomplete state of 

 knowledge it would seem that nothing is to be gained by removing 

 any of the forms from Synchytrium. Considerable doubt exists 

 as to just how much importance is to be attached to the differ- 

 ences in sporangial formation which constitute the basis for the 

 above key to subgenera. If the extrusion of the thin-walled 

 vesicle should prove to be inconstant in some species, as has been 

 shown to be the case in Phytophthora, the above separation could 

 not be maintained. In any case, the genus as it stands consti- 

 tutes a coherent whole. 



Fig. 16.- — Synchytrium taraxaci de Bary & Woronin on Taraxacum, (a) 

 Sorus of swarnisporangia. (6) Single swarmsporangium, more enlarged, 

 germinating. {After de Bary and Woronin 1865.) 



As representative of the subgenus Eusynchytrium the species, 

 S. taraxaci de Bary & Woronin (1863: 22), occurring in Europe, 

 Australia, and North America on Taraxacum, may be discussed 

 (Fig. 16). In it several generations of swarmspores are formed 

 during the summer, and only the last develop into resting spores. 

 The earlier generations form summer sori of sporangia. The 

 sorus is enclosed in a definite membrane, and at maturity con- 

 tains fifteen to twenty sporangia. Though there is usually 

 only one sorus in a single host cell there may be several. The 

 sporangia are very unequal in size, are irregularly polyhedral 

 from mutual pressure, and when fully formed have a thick 

 hyaline wall and reddish orange contents. The swarmspores 

 are freed on the living host and reinfect it. Each swarmspore 

 is globose, uniciliate, and contains one or more reddish oil 

 globules. The resting spore formed at the close of the season 

 lies free in the host cell, is globose, and at maturity is provided 



