Fungous Flora of the Soil 



463 



Family Thamnidiaceae 



Thamnidium elegans Link, Observ. in Ord. Plant. Nat. i: 45; Berliner 

 Magaz. Naturf. Freunde 3:21. 1809. Fischer, Rab. Krypt. Flora Abt. 

 4, i: 241-244. fig. 41. 1892. 



Sporangiophores erect, ending in large 

 sporangia. Below these, in the middle or 

 under part of the sporangiophore are generally 

 2-5 verticillate horizontal side branches that are 

 forked several times (2-10) after an obtuse- 

 angled fashion. The branchlets finally end 

 in sporangioles. The whole sporangiophore 

 is usually 0.5-3 cm. occasionally 6 cm. high 

 by 25-35^ thick. The white floccose group of 

 forked verticillate branches are relatively very 

 small, 0.25-1 mm. broad. The main verticillate 

 branches up to the forking are 150-200/z long by 

 8/u thick; the forks of the first order are 40-60/x 

 long; the forks of the last order are only 4-6^1 

 long by 2yu broad. The membrane of the 

 sporangiophore and its branches is colorless and 

 smooth ; contents are also colorless. Branching 

 of the sporangiophore is very variable (see 

 variation below). Chief sporangia (haupt- 

 sporangia) globose, large, ioc-200/i diameter, 

 occasionally smaller, at maturity white with 

 large ovate or bell-shaped, colorless, smooth 

 columella; sporangioles globose, small, white, 

 8-1 6iU in diameter, mostly 4-spored, varying, 

 however, from i to 10; spores of haupt- 

 sporangia and sporangioles similar and equally large (except in the 

 one-spored sporangioles where they are globose, 8-1 6/x), ellipsoidal, 

 8-1 o/x by 6-8^1, smooth, weak gray-brown. Zygospores are globose, 

 black, with thick black warty exospore and yellowish endospore. 

 Zygospores not observed in our cultures. 



Hab. Isolated from pepper root taken from soil of plant-breeding 

 plats of Cornell University, Ithaca, N. Y., March, 191 1, by the writer. 

 Plant pathology herbarium No. 5,904. 



Variation of sporangiophores. — The branching of the sporangiophores is 

 very variable. In one extreme case the sporangiophore carries only the 

 chief sporangium, when it resembles an ordinary Mucor; in the other case 

 the chief sporangium is wanting, the sporangiophore ending then either 

 with a crown of sporangioles or with a sterile tip. Occasionally the first 



Fig. 1 10. — Thamnidium ele- 

 gans Link. A, sporangio- 

 phore and hauptsporangia, X 

 60; B, sporangiophore and 

 nebensporangia, x 60; C, 

 spores from tiehensporangia, 

 X 2j6.6; D, ultimate divi- 

 sions of sporangiophore, 

 with sporangioles, x 2j6.6; 

 E, columella of haupl- 

 sporangium, x 2j6.6 



