56 



PLASMODIOPHORALES 



PLATE 10~Continned 



Spongospora Campanulae 



Spoil (jospora Ciimpnnulae 



Fig. 38. Campanula rapiinculoules with numerous jfalls 

 and nodules on roots. Ferdinandsen and Winge, "JO. 



Fig. 39. Young parasite with nuclei dividing "promitoti- 

 cally." F. and W., I.e. 



Fig. 40. Multinucleate Plasmodium. F. and W., I.e. 



Fig. 41. Plasmodium enveloping host nucleus. F. and W., 

 I.e. 



Fig. i-2. Irregular cystosorus. F. and W., I.e. 



Fig. 43. Section through a cystosorus. F. and W., I.e. 



Fig. 44. Section through two resting spores showing 

 finely punctate warty walls. F. and W., I.e. 



and Ledingliam ('35) observed only one zoospore. 

 Furthermore, all earlier investigators figured and 

 described the zocspores as uniflagellate, but Led- 

 ingliam demonstrated conclusively that they are bi- 

 flagellate and heterocont (fig. 7, 8). Whether the 

 flagella are attached at or near the anterior end is 

 not definitely known. Massee, Kunkel, Osborne 

 ('11 ) and Home ('30) held that the plasmodium is 

 formed by the fusion of several amoebae (fig. 19). 

 but they were not certain whether such amoebae arise 

 by division of a single amoeba within the infected 

 host cell or are the result of infection bv several 



amoebae. Cook ('33), on the other hand, contended 

 that the plasmodium is initiated by the fusion of 

 gametes in pairs (fig. 20-22). 



There is also difference of opinion about infection 

 and spread of parasite in the host tissue. Massee and 

 Cook in particular held that the amoebae have the 

 ability to penetrate the host cell walls and thus pass 

 from cell to cell, spreading the infection. Osborne 

 and Home, in contrast, maintained that the amoebae 

 are incapable of boring through the walls and are 

 distributed passively and fortuitously by division of 

 the infected cell (fig. 14). Kunkel, however, reported 

 that the primary infection of young tubers as well as 

 secondary infection of tissues around old sori occurs 

 by invasion of the plasmodium. The latter passes 

 through and between the epidermal cells, and once 

 beneath the epidermis it spreades out in all directions 

 (fig. 17). Johnson ('09) believed that the plasmo- 

 dium may migrate from the diseased parent tubers 

 into the stem and stolons of the young plants, and 

 eventually infect the young tubers. Massee thought 

 that the plasmodium might encyst during the cold 

 winter season and renew its activities when the 

 tubers began to sprout. \\'ild ('29) considered the 



