CLASS ARCHIMYCETES 



23 



the auxiliary hosts are from Potentilla, Valeriana, Hypericum, Epilobium 

 and Myosotis; or in the alpine saxifrage groups (S. Saxifragae) the princi- 

 pal host is »S. aizoides, the auxiliary hosts S. stellaris, S. moschata, Andro- 

 sace chamaejasme, Hutchinsia, Leontodon, Viola, Ranunculus, etc. 



In Synchytrium Succisae, on Succisa pratensis, there is a division of 

 labor between the summer sori and the resting spores; the summer sori 

 remain thin walled and only the somewhat smaller hypnospores, in which 

 the fungus winters over, possess a thick double-layered sheath (Rytz, 

 1907). 



In Synchytrium (Eusynchytrium) Taraxaci on Taraxacum sp. (Schroe- 

 ter, 1875; Liidi, 1901), S. {Eusynchytrium) decipiens on tropical and 

 temperate phanerogams (Tobler-Wolff, 1912) and S. (Eusynchytrium) 

 Puerariae on Pueraria Thunbergiana in Japan (Kusano, 1907, 1908), the 

 stage of the projecting blister is omitted; their zoospores arise in the 



Fig. 12. — Synchytrium aureum. Hypno- 

 spore in an enlarged epidermal cell, sur- 

 rounded by a small gall. ( X 93 ; after Rytz, 

 1907.) 



Fig. 13. — Synchytrium Saxifragae. Hy- 

 pnospore, a; with sorus, b, which has 

 already formed zoosporangia. (X 340; 

 after Rytz, 1907.) 



initial cells themselves and swarm out of them through an opening. In 

 S. decipiens, cleavage of the protoplasm produces uninucleate portions 

 which form the young naked sporangia. They are called protospores 

 (Harper, 1899). Their nuclei divide repeatedly so that every sporangium 

 contains several nuclei. In this species, four chromosomes have been 

 counted (F. L. and A. C. Stevens, 1903; Griggs, 1909). In »S. Taraxaci 

 the protospore stage is omitted and the multinucleate protoplasm, as in 

 S. endobioticum, is divided directly into multinucleate sporangia whose 

 nuclear number further increases by division (Dangeard, 1891; Harper, 

 1899) ; this division takes place by cleavage from the periphery inwards, 

 not by successive formation of membranes as in S. endobioticum. 



A fourth subgenus Woroninella is distinguished by the crateriform 

 or aecidial habit of its open sori. So far only thin-walled summer spores, 

 germinating as in the Eusynchytrium type, are known. Synchytrium 

 Psophocarpi in tropical Asia is parasitic on Psophocarpus tetragonolobus, 

 S. vidcanicum on Lespedeza cytisoides, S. aequatoriense in Ecuador on 



