Poitnd: REVISION OF MUCORACEAE. 99 



tionship quite evident. Other forms, showing a tendency to 

 lose the terminal sporangia and producing side branches w ith 

 sterile tips, connect with the Chaetocladieae. 



7. THAMNIDIUM Lk. Obs., 1 : 31, 1809. 



Chaetostylum Vak Tiegh. and Le Mon. Ann. Sc. Nat. v. 17 : ,328. 



1873. ' 

 Helicostylum Corda. Ic. Fung. 5: 18. 1842. 



Sporangiophores erect: principal sporangia terminal on the 

 main branches, with a columella; sporangiola on side branches, 

 without a columella. 



Schroeter unites Thamnidium, Chaetostylum, Sind Helicostylum, 

 calling the two latter subgenera. 



In Euthamnidium the side branches are simple or dichotom- 

 ously branched, the ends bearing sporangiola. The type is T. 

 elegans Lk. 



Thamnidium paradoxum (B. and C.) Berl. and De Toni. Syl. 

 Fung. VII. 1 : 211=Mucor paradoxusB. and C. N. A. F. No. 377, if 

 a Thamnidium, probably belongs to this species as the size and 

 shape of the spores and the habitat agree with it fairly well. 

 But it seems more likely that it is only a form of Mucor mucedo, 

 as the description states that the smaller sporangia are borne 

 on hyphae arising from the mycelium. M. mucedo often at first 

 produces small dwarfed sporangia which are followed by the 

 larger normal ones. Fischer observes that the abnormalities 

 of M. mucedo have been freely described as species by the 

 earlier mycologists. 



In the subgenus Chaetosii/lum the principal sporangia are 

 often wanting, and sporangiola are produced on small branch- 

 lets arising from the swelling below the tip. The only species 

 is T.fresenii (Van Tiegh, and Le Mon.) Schroet. 



In the subgenus Helicosti/lum the side branches terminate in 

 sterile tips and bear sporangiola on spirally coiled branchlets. 



The type species is: 



Thamnidium helicostylum (Bonorden.) 



Helicostylum elegans Corda. 1842. 1. c. 



Pleurocijstis helicostylum BoN. Hbk. Alg. Myc. 124. 1851. 



/l.scop/iora a;)icena Preuss. Linnaea 2/»: 77. 18.52. 



Hiamnidium amoenum (Preuss.) Sciiroet. Pflanzenfaru. i. 1 : 128. 



