44 



PLASMODIOPHORALES 



swollen root hairs and occasionally form almost 

 spherical, oval and elongate hollow cystosori. 



Sorosphaera radicalis lias been found only in root 

 hairs and does not attack the other tissues of the root. 

 Hence no external symptoms of the disease are visi- 

 ble on the host plant except a slight reddening of the 

 stem and leaf bases. When the infected root hairs 

 decay, the cystosori are liberated into the soil. In- 

 fection by zoospores api)arently occurs during the 

 early developmental stages of the root hairs. 



.Although Cook and Schwartz failed to count the 



chromosomes, they nonetheless believed that meiosis 

 occurs during the first of the two last divisions pre- 

 ceding sporogenesis. No evidence of gametic fusion 

 has been observed. 



Cook and Schwartz reported that at the conclusion 

 of promitosis "a wall is now secreted around the 

 Plasmodium, and the whole mass passes into a spor- 

 ing stage." If this statement and observation are 

 true, it is obvious that .S'. radicalis differs radically 

 in this respect from all other known species of the 

 Plasmodiophorales. 



PLATE 6 



Sorosphaera Veroiiicae 



Fig. 1. Vcroiiira chamaedrys with galls caused by S. 

 t'eronicae. Winge, '13. 



Fig. -2. Hypertrophied host cell with six plasmodia. Note 

 relative sizes of healtliy and infected cells. Blomfield and 

 Schwartz, '10. 



Fig. 3. Hypertrophied ho.st cell with five plasmodia. Four 

 host nuclei in telophases of division. Blomfield and 

 Schwartz, I.e. 



Fig. i. Nucleus of parasitized cell witli numerous nu- 

 cleoli. Blomfield and Schwartz, I.e. 



Fig. 5. Lobed and distorted nucleus of an infected cell. 

 Maire and Tison, "09. 



Fig. 6. Old host cell with four cystosori; protoplasm 

 almost completely gone. Blomfield and Schwartz, I.e. 



S. rfi(UcaUs 



Fig. 7. Hypertrophied root hair with cystosorus in sur- 

 face view. Cook and Schwartz, '29. 



Fig. 8. Median longitudinal section of an ellipsoidal 

 cystosorus. Cook and Schwartz, I.e. 



S. f'erontcae 



Fig. 9. Uninucleate stage of thallus. Maire and Tison, I.e. 



Fig. 10. Resting nucleus of young parasite. Blomfield 

 and Schwartz, I.e. 



Fig. 11. Beginning of promitosis of a 4-nucleate Plas- 

 modium with centro.somes and astral rays. Maire and 

 Tison, i.e. 



Fig. 12. "Saturn stage"' of promitosis. Maire and Tison, 

 I.e. 



Fig. 13. Early anaphases. Maire and Tison, I.e. 



Fig. 14. "Double-anchor" stage of promitosis. Maire and 

 Tison, I.e. 



Fig. 1.5. I.ate anaphases with centrosomes and asters. 

 Maire and Tison, I.e. 



Fig. Hi. I.ate prophase of vegetative nuclei in Plasmo- 

 dium with four chromosomes. Webb, '3.5. 



Fig. 17. Later stage sliowing four split chromosomes. 

 Webb, I.e. 



Fig. 18. Four chromosomes arranged in a ring around 

 constricting nucleole. Webl), I.e. 



Fig. 19. Metajjhase; daughter chromosomes beginning to 

 separate. Webb, I.e. 



Fig. 20. Early anaphase. Two rings of four chromosomes 

 each moving apart. Webl), I.e. 



Fig. 21. Later ana])liase. Webb, I.e. 



Fig. 22. Telophases of jiromitosis. Maire and Tison, I.e. 



Fig. 23, 2i. Schizogony of jilasmodium ; uni- and binucle- 

 ate segments respectively being split off. Maire and Tison, 

 I.e. 



Fig. 25. Beginning of akaryote stage; chromatin passing 

 out into cytoplasm. Blomfield and Schwartz, I.e. 



Fig. 26. Akaryote stage; nuclei clear and vacuole-like. 

 Blomfield and Schwartz, I.e. 



Fig. 27. Reconstructed nuclei following akaryote stage. 

 Blomfield and Schwartz, I.e. 



Fig. 28. Later stage showing reappearance of nucleoli 

 and chromatin. Maire and Tison, I.e. 



Fig. 29. So-called "garland" stage of reconstructed nu- 

 clei. Maire and Tison, I.e. 



Fig. 30. Same stage highly magnified. Winge, I.e. 

 Fig. 31,32. Synezesis (?). Maire and Tison, I.e. 

 Fig. 33. Beginning of cleavage into spore mother cells; 

 appearance of nuclei suggestive of diakinesis. Maire and 

 Tison, I.e. 



Fig. 34. Early diakinesis. Webb, I.e. 



Fig. 35. Diakinesis with four pairs of homologous chro- 

 mosomes. Webb, I.e. 



Fig. 36. Equatorial plate stage of heterotypic division 

 during sporogenesis. Cleavage into spore mother cell com- 

 plete. Maire and Tison, I.e. 



Fig. 37. Same stage. Winge, I.e. 



Fig. 38. Late anaphases of meiotic division; first division 

 of spore mother cells beginning. Maire and Tison, I.e. 



Fig. 39. First division of spore mother cells complete. 

 .Maire and Tison, I.e. 



Fig. 40. Late prophase nucleus of second or homeotypic 

 division with four chromosomes. Webb, I.e. 



Fig. 41. Equatorial plate stage of second division during 

 sporogenesis. Maire and Tison, I.e. 



Fig. 42. Second cell division into incipient resting spores. 

 Fig. 43. Incipient resting spores aggregating into a 

 globular mass; initial stage in formation of cystosorus. 

 Maire and Tison, I.e. 



Fig. 44. Later stage in cystosorus development; spores 

 arranged at periphery with a viscous substance in the cen- 

 ter. Maire and Tison, I.e. 



Fig. 45. Young cystosorus in median section with well- 

 defined walls around spores; remants of viscous substance 

 in center. Maire and Tison, I.e. 



Fig. 46. Cystosorus in median section. Blomfield and 

 .Scbwartz, I.e. 



Fig. 47. Portion of a cystosorus in surface view. Blom- 

 field and Schwartz, I.e. 



Fig. 48. Urn-shaped resting s])ore witb apical collar. 

 Winge, I.e. 



Fig. 49. Binucleate resting spore. Maire and Tison, I.e. 

 Fig. 50. Division of nuclei in binucleate resting spore. 

 .Maire and Tison, I.e. 



Fig. 51. Trinucleate resting spore. Maire and Tison, I.e. 



