584 COMPARATIVE MORPHOLOGY OF FUNGI 



of aecial formation. The eu- and -opsis forms are called long-cycled 

 forms, the other (endo-, brachy- and micro- forms) are called short-cycled 

 forms. In the endo- type (0, I) both urediniospores and teliospores are 

 lacking, e.g., Endophyllum Sempervivi on Sempervivum. The uninucleate 

 mycelium penetrates the whole leaf parenchyma and winters over in the 

 host. It first forms pycnia, then aecia. Plasmogamy occurs in the aecia, 

 as was earlier shown, with consequent dicaryons which fuse in the 

 aeciospores. These germinate (normally) with basidia whose spores 

 again infect Sempervivum leaves. In the endo- type accordingly, the 

 aeciospores have taken over, caryologically and biologically, the func- 

 tion of teliospores. The life cycle may be indicated as follows: 



iPycnium— »Pycniospores PC R 



Uninucleate— »»Aeciuijn— *Sexual cells— ^Aeciospores— >-Basidia— *Basidiospores 

 mycelium 



Diagram XXXIV. 



The gametophyte is formed as in the eu- forms, while the sporophyte 

 has lost its individuality : it is limited to the aeciospores, on whose germi- 

 nation meiosis takes place. Its height of development places it at the 

 same stage as the diplonts of the Phycomycetes. 



In contrast to the endo- forms, the brachy- and micro- forms are 

 distinguished by the lack of aecia, the micro- forms by the further lack 

 of uredinia. As far as the brachy- forms (0, II, III) have been investi- 

 gated, a typical sexual act occurs in the uredinium which takes the place 

 of the aecium in the life cycle. In Triphragmium Ulmariae the basidio- 

 spores germinate to a uninucleate mycelium. On this are formed pycnia 

 and large primary uredinia of irregular shape. In the latter, sexual acts 

 occur, the spores of the primary uredinium again infect plants of Ulmaria 

 and develop there to binucleate mycelia which form small, rounded, 

 secondary uredinia and later telia. Its life cycle proceeds according to 

 the following scheme: 



Basidiospores 



/Pycnium — tPycniospores 



/ P 



/ Primary 



Uhinucteat£H*Primary-»Sexual cells-^TJrediniospores->Brnuc 



AJrcdmiospores 

 / C R 



eate*-»Teliospores— +-Basidia 



mycelium Uredinium mycelium 



Diagram XXXV. 



It is essentially correct even to pycnia, often absent as in the eu- 

 forms, but the primary uredinia are substituted for aecia. 



