URE DIN ALES 571 



the second or third cells from the outer ends of the chains, the separating 

 walls completely disappearing. At the same time the buffer cells above 

 collapse, like the disjunctive cells in the uredinium. The fusion cell 

 divides immediately, the upper cell taking most of the cytoplasm, leaving 

 the lower cell vacuolate. This upper cell then forms a short chain of 

 binucleate cells which occupy the space below the peridium. Caryogamy 

 begins in the terminal cell of these chains and proceeds slowly basipetally. 

 The now uninucleate zeugite elongates and forms the typical four-celled 

 basidium of the Auricularia type. After the basidiospores have been 

 shed, the basidium collapses and the cell below elongates and forms a 

 basidium. This process may continue until all the binucleate cells are 

 used up, but age of the sorus and mechanical difficulties in raising the 

 lower basidia high enough to secure complete dissemination of basidio- 

 spores, usually results in the failure of the lowest cells to function 

 properly. 



Here we have the diploid phase and the binucleate mycelium reduced 

 to its lowest possible amount, without even the differentiation of telio- 

 spores as such, consequently this species in some ways seems more primi- 

 tive than Septobasidiwn and might be placed in Auricularia, except 

 for the catenulate basidia. Similarly the so-called teliospores of Coleo- 

 sporium are rather to be regarded as thick-walled basidia. The sorus 

 consists exclusively of fertile basidia, while in Auricularia there are sterile 

 paraphyses. Similarly the sorus should be regarded as basidial hymen- 

 ium, not telium. In order not to confuse their terminology, however, 

 systematists have used teliospore for structures which appear in the same 

 position as true teliospores do in other rusts. These "teliospores" 

 germinate "internally," directly to basidia. From the standpoint of 

 comparative morphology, it must be emphasized that the Coleosporiaceae 

 lack teliospores. 



Melampsoraceae. — As the Coleosporiaceae correspond to the Auricu- 

 lariaceae, this family exhibits the developmental tendency of the Septo- 

 basidiaceae. The zeugites increase in independence and become special 

 storage organs in which the nutrients are prepared for the moment most 

 favorable to basidial formation. The basidia agree extensively in their 

 habits with Septobasidium, and are without stipes, lateral or terminal 

 on hyphae; only they are formed (as is the character of the rusts) 

 endoparasitically, exclusively within the host instead of upon its surface. 



In Uredinopsis (Faull, 1928), the teliospores arise in scattered groups 

 just below the epidermis, occasionally a few in the mesophyll. They 

 have a thin, hyaline, smooth membrane and are spherical or elongate, 

 septate and capable of germination early the following spring (Fig. 382, 2). 



In Melampsorella, they are similar but are formed within the epider- 

 mal cells and, in case several are laid down in the same cell and the space 

 is not sufficient, they are flattened sidewise. They develop on new leaves 



