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GENERAL MORPHOLOGY OF PLANTS 



shown the life cycles of rusts having fewer spore forms. For 

 example, some lack the uredo stage, as in Puccinia podophylli on 

 the mandrake; others lack the aecidial stage, as in. Puccinia taraxaci 

 on the dandelion; while still others lack both ascidia and uredo, 

 having only the spermogonia and teleuto stage, as in Puccinia 

 malvacearum, the rust of the hollyhock. 



Diagram III. Illustrating life cycle in the development of the four different form cycles 

 in the rusts. The heavy-walled oval bodies enclosing the bold face No. Ill represent the 

 primary teleutospore. The circles with the bold face No. I represent the primary aecidium. 

 The circles with the short radiations or spines with bold face No. II represent the primary 

 uredo, and the lighter Nos. 1, II, III in the figures represent the corresponding secondary 

 ascidium, uredo and teleutospore stages which are propagative, and thus repeat the cycle. 

 The small circle connected with the teleutospore by a short, narrow line represents the 

 promycelia and sporidia. The narrow line issuing from the sporidium represents the my- 

 celium of the aecidial stage, the cells of which are uninucleate. The small elliptical body 

 connected with this line by a narrow, short line represents the spermogonium; the cells of 

 this are also uninucleate. The broad lines represent the mycelium produced by the germi- 

 nation of the ascidio- and uredo-spores. In reading the cycle pass from left to right. 



A represents the cycle of those species having all four spore forms. B represents the 

 cycle of those species in which the uredo stage is absent. C represents the cycle of those 

 species in which the secidium is absent. D represents the cycle of those stages in which 

 both the ascidium and uredo are absent. 



