32 BOTANICAL GAZETTE [july 





Summary 



. i. The essential features in the development of the cup are 

 similar to those found in the development of the caeoma. The 

 initial hyphal mass, or primordium, is formed by hyphae growing 

 radially toward the center of the future cup. 



2. The cup is more deeply seated and produces a greater number 

 of sterile cells and gametes to each gametophoric hypha. The 

 gametes form a fertile layer two or more cells in thickness. The 

 sterile cells that form the pseudoparenchyma of the cup are 

 homologous with the " buffer" cells of the caeoma. 



3. Sexual cell fusions, by the breaking down of the cell walls 

 between two equal gametes, were found in 6 additional species of 

 cupulate aecidia, namely Ur. Caladii, P. Claytoniata, P. Violae, P. 

 Hydrocotyles, P. Eatoniae, and P. angustata. Although the actual 

 fusion stages were not seen in the last named species, the presence 

 of two-legged basal cells is evidence that the fusions are of the same 

 type as those found in the other species. No central organs 

 ("fertile hyphae ") or multinucleated cells were found. The organi- 

 zation of the cup, therefore, is merely that of a remarkably unified 

 colony of gametophores. 



4. Triple cell fusions w r ere observed in P. Claytoniata and P. 

 Violae, and trinucleated aecidiospores were frequently found in 

 both of these species and in Ur. Caladii. Several quadrinucleated 

 aecidiospores and a chain of quadrinucleated cells were found in 

 P. Claytoniata. 



5. The first fusion cells are formed at the center of the gametic 

 tissue, and the subsequent ones are formed on all sides of this center 

 in centrifugal order, until the lateral borders of the aecidium are 

 reached. 



6. The fusing cells may have their long axes in general in the 

 long axis of the cup, for example P. Claytoniata, P. Violae, P- 

 Hydrocotyles, and Ur. Caladii, or tangential to its curved basal 

 surface, for example P. Eatoniae. 



7. The presence or absence of a peridium is a natural but not 

 very fundamental distinction between the aecidium cup and the 

 caeoma. The production of a peridium is correlated with the deep 

 location of the cup and the extensive formation of sterile cells. 



