MU COR ALES 257 



In recognizing the above subgenera the treatment of Schroter 

 (1893: 127) is followed. The groups were originally described 

 as separate genera, and are given generic rank by Fischer (1892: 

 246). They are clearly very closely related, and intermediate 

 species and intergrading conditions occur (Brefeld 1881: 58; 

 Bainier 1906 : 210). For descriptions of American species consult 

 Sumstine (1910), Pound (1894), and Povah (1915). The striking 

 beauty of the sporangiophore in the genus renders it a favorable 

 subject for class use. 



The genus Actinomncor Schostak. (1898: 155), placed by 

 Lendner near Thamnidium, is known only from the original 

 description. It is here regarded as a doubtful form. 



Chaetocladiaceae 



Sporangia and sporangiola lacking, replaced by unicellular 

 conidia, which cover sub-terminal enlargements of branches of 

 the conidiophore; zygospore not enclosed in a hyphal envelope. 



A single genus. 1. Chaetocladium (Fig. 91). 



1. Chaetocladium Fresenius (1863: 97). 



Mycelium parasitic on other members of the Mucorales, wide- 

 spreading, profusely branched; point of attachment to host hypha 

 marked by a dense cluster of peculiar vesicular outgrowths 

 (Burgeff, 1920) ; fertile hyphae repeatedly branched; the branches 

 tapering to long, sterile, sharp-pointed tips, many of which are 

 provided with small subterminal swellings covered with sterig- 

 mata bearing conidia; conidia globose, unicellular; zygospores 

 globose, formed between the ends of the copulating gametangia 

 as in Rhizopus. 



The genus contains two species, C. jonesii (Berk. & Broome) 

 Fresenius (1863: 97) [C. fresenianum Brefeld, 1881: 55] based on 

 Botrytis jonesii Berk. & Broome (1854: 462), and C. hrefeldii 

 van Tieghem & le Monnier (1873: 342) based on a form which 

 Brefeld (1872: 29) had discussed under the name C. jonesii. The 

 two species are very similar, the conidia of the first being spiny 

 at maturity and measuring six to eight microns in diameter, 

 while those of the second are smooth and smaller (two to four 

 microns). 



The conidia of Chaetocladium are frequently termed mono- 

 sporous sporangia or sporangiola. This terminology is based 



