12 BOTANICAL GAZETTE {july 



Triph 



my 



pro 



duced above each gamete in the caeoma of Melampsora 

 Further, I have found cases of two gametes borne one above the 

 other in the same hypha in this form (12, pi. 9, fig. 18). Melamp- 

 sora Lini thus seems to be an intermediate form between the more 

 simple caeomas, with but one sterile cell and gamete to each hypha, 

 and the aecidium cup with several sterile cells and gametes. It 

 should be mentioned in this connection that the sterile cells of the 

 cup can scarcely be considered to function as " buffer" cells in the 

 sense that Christman (7) used the term. If any function is to be 

 ascribed to them, it is apparently that of space making. Their 

 disintegration provides room for the development of the spores. 



Up to this point in the development of the cup no multinucleated 

 cells were seen, nor any other large cells that could in any way be 

 considered central cells or organs from which the gametophoric 

 hyphae might have arisen. Careful search was made for them in 

 all stages in all of the forms included in this work, as well as in some 

 additional forms. My observations do not agree, therefore, with 

 those of Massee (20) as to the presence of central organs, nor with 

 Richards' (27) as to the presence of a " fertile hypha/' nor do I 

 find the multinucleated cells of Olive (22). I am confident that 

 these multinucleated cells do not normally occur in any of the 

 forms that I have studied. It is possible that they are peculiar to 

 certain types of aecidia only. 



The conditions found in the development of the aecidia of the 

 other species investigated up to the time of the fertilization stage 

 are very similar to those described for P. Claytoniata. Excepting 

 minor differences, such as involve the form and size of the cup, its 

 position in the leaf tissue, the relative extent of the pseudoparen- 

 chyma, and the number and position of the gametes, the general 

 morphological development of all is of the same nature. The same 

 excavation of the mesophyll of the host in areas of varying size and 

 shape, and the same sterilization of radial hyphae to form the 

 pseudoparenchyma are found in all. 



The most noticeable difference found is in the position of the 

 gametes. P. Violae is more like P. Claytoniata in this respect, and 



