MUCORALES 



99 



ably, and their nuclei divide repeatedly. In forms with stolons, the sporangio- 

 phores branch almost exclusively from the nodes and are then firmly attached 

 to the substrate by the group of rhizoids, but in Ahsidia they may branch 

 directly from the stolons midway between nodes. 



In the simpler species the sporangiophores are unbranched (Fig. 4, 7) ; in 

 the more highly organized, they are forked, racemose, corymbose, cincinnal, 

 etc. (Fig. 4, 3, 9). The tip of each branch swells up to a sporangium, allowing 



Fig-. 4. — Sporangia. 1, Ahsidia Truchisi (after Lucet & Costantin) ; 2, Pirella circinans 

 (after Bainier 1883) ; 3, i, Circinella umhellata, showing dehiscence and columella (after 

 Tieghem 1873); 5, Mucor Mucedo (after Brefeld 1872); 6, Rhisopus niger (after Bainier): 

 7, Rhisoims reflexus (after Bainier 1883) ; S, Rhizopus parasHicus (after Costantin 1900) ; 

 9, Sporodinia grandis (after Lendner 1908). 



the protoplasm of the swollen hyphal portion to migrate into it, and is finally 

 abjointed (cut off by a septum). In the tribe, Mortierelleae, the septum is 

 plane or slightly convex, in the Mucoreae it forms a dome projecting far into 

 the sporangium. This dome is usually called a columella. It is generally 

 smooth, cylindric or pyriform and remains attached to the stalk long after the 

 spores are shed. In Piloholus roridus (Tieghem 1875) and Pilaira anomala 



