6 Bulletin 313 



Plasmodiophora brassic^ Wor. — On the roots of cabbage, cauli- 

 flower and related plants. Causes enlargement of the infected parts 

 which are commonly known as "club root" or "finger and toe" dis- 

 ease. The organism lives within the parenchyma cells and stimulates 

 both the infected and the neighboring cells. The medullary rays 

 and cortex become thickened; the sclerenchyma cells suppressed, 

 xylem reduced, and the phloem increased. 



1. Diseased cabbage seedling. 2. Diseased root of older plant. 3. Cross- 

 section of diseased root showing organisms within certain cells, 2/3. 4. Plas- 

 modium in cells, 1/6. 5. Plasmodium in 4 distinct divisions showing multi- 

 nuclei, 1/6. 6. First stage in the formation of spores, 1/6. 7. Second stage 

 in the formation of spores, 1/6. 8. Mature spores, 1/12. 9. Division of 

 spores, 1/12. 



Synchytrium vaccinii Thomas. — On the cranberry and also on 

 Gaultheria procumhens, Cassandra caJyculata, Kalmia angustifolia, 

 Azalea viscosa, Clethra alnifolia and Gaylussacia sp. and Vaccinium 

 corymbosum. Causes small red galls on stems, leaves, flowers and 

 fruits of cranberry and other hosts. Mycelium absent or scanty, 

 producing the globose sporangium within the center of the gall ; 

 many motile swarm spores produced from the sporangium. 



10, 11, 12. Galls on various parts of cranberry plant. 13. Cross section of 

 the leaf and gall, 2/3. 



Saprolegnia ferax* (Gruith) Thuret. — Grows freely on dead 

 flies in water. The slender hyphse show few septa until the tips are 

 cut off in the formation of the sporangia. Zoosporangia clavate- 

 cylindrical. The zoospores are almost spherical or slightly pear- 

 shaped, biciliate and very active. After the emergence of the zoo- 

 spores, there is a growth from the base cell into the old sporangium. 

 No oospores were observed. 



14. Dead fly covered with the fungus. 15. The immature sporangia, 2/3. 

 16. Two stages in formation of the spores, 1/6. 17. Emerging of the zoo- 

 spores and the new growth into the old sporangium, 1/6. 18. Zoospore, 1/12. 



Albugo bliti (Biv.) Kuntze. — O leaves of .hnarantlius hy- 

 bridus, A. chlorostachys, and other species of Amaravthaceae. 

 Causes white to yellowish, prominent, superficial, circular spots, 

 1-10 mm., which are sometimes confluent. Conidiophores hyaline, 

 cylindric, about 15 x 60 /i,. Conidia hyaline and nearly spherical, 

 8-15 X 15-20/.. 

 19. Conidia. 



* Syn. 5". ferax Amct. 



Achlya prolifera Pruigsh. 

 S. ihnretii de Bary. 



