IO BOTANICAL GAZETTE [july 



continues toward the lateral and basal surfaces. The hyphae that 

 run from the basal surface of the mass to its center are on the aver- 

 age about 10 cells in length, while those that run from the lateral 

 surfaces are somewhat shorter. Fig. i shows a section through the 

 lateral surface of a young hyphal mass in which the sterilization 

 of 3 or 4 of the apical cells of the hyphae has been accomplished. 

 At the top of the figure the border of an epidermal cell, marking the 

 apical surface of the mass, is indicated by a double line, and a cell 



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Fig. i. — Formation of the pseudoparenchyma in the aecidiumof P.Claytoniata: 

 the attachment of the forming pseudoparenchyma cells (x) with the hyphae on which 

 they are borne is evident. 



nuclei are larger, with larger nucleoles, and their cytoplasm is con- 

 siderably denser. Several layers of hyphae at the base of the 

 figure that run tangentially to the curved basal surface of the mass 

 are seen to give rise to the perpendicular hyphae that bear the dif- 

 ferentiated, well nourished cells. The perpendicular hyphae shown 

 in the figure average about 6 or 7 cells in length and have apparently 

 cut off 3 or 4 sterile cells each. The sterilization process continues 

 until only 4 or 5 cells at the bases of the perpendicular hyphae 



remain 



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the 



mass. The remaining cells of the perpendicular hyphae now stand 



