PHYCOMYCETEAE 



Fig. 49. Mucorales, Family Mortierellaceae. Mortierella rostafinskii Bref. (A) 

 Sporangium. (B) Hyphal cluster at base of sporangiophore. (C-E) Stages in production 

 of zygospore. (A-B, after Brefeld und von Tavel: Untersuchungen aus dem Gesammt- 

 gebiete der Mykologie, Heft 9, pp. 1-156, Miinster i. W., Heinrich Schoningh. C-E, 

 after Brefeld: Botanische Untersuchungen iiber Schimmelpilze, Heft 4, pt. 5, pp. 81- 

 96, Leipzig, Arthur Felix.) 



sexual reproduction is left unconsidered, but they probably indicate in 

 general the directions that the modifications followed. 



The simplest and probably the most primitive type of sporangium is 

 that found in the genus Mortierella. It must not be understood that this 

 genus is considered to be the most primitive of the Mucorales, for in its 

 sexual reproduction it is so much modified from the more typical repre- 

 sentatives of the order that it is clearly to be recognized as well advanced 

 in evolution. However, in its sporangial development it seems to have 

 retained a very primitive structure. This is merely one of the very many 

 cases where evolution has advanced far along certain lines of development 

 (in this case the manner of sexual reproduction) while remaining about 

 at a standstill in its mode of asexual reproduction. The sporangium is a 

 spherical enlargement of the apex of the sporangiophore, set off from the 

 latter by a cross wall at the point where the enlargement begins. In 

 sporangial evolution the next step appears to have been the development, 

 as in Mucor, of a "columella." This in reality represents a displacement of 

 the septum separating the sporangium from the sporangiophore so that it 

 arches up into the former. The columella is laid down in the position it is to 



