B AS IDIOM YCE TES 



389 



and forms on the surface a hymenium of club-shaped basids each of 

 which produces four basidiospores. The spores divide at maturity trans- 

 versely into four cells, only the two end cells of which germinate, doubt- 

 less at the expense of the contents of the remaining two. The germ- 

 tubes penetrate the epiderm of the leaf of the host, and a new mycele is 

 formed which again bears basids. If, however, germination takes place 

 elsewhere than on the proper host-plant, and conditions for the vegeta- 

 tion of the fungus be otherwise favour- 

 able, the germ-tube begins to sprout in- 

 definitely by means of elongated sprout- 

 cells^ giving rise to others only at the ends. 

 This condition has been maintained in nu- 

 trient solutions for a considerable time, but 

 the sprout-cells have never been observed 

 actually to give rise to a new mycele like 

 the one produced by the basidiospores. 



The Tremelline^ (Tremella, Dill., 

 Exidia, Fr.) present another simple type. 

 They are gelatinous fungi of not very 

 definite form, commonly of wavy outline, 

 and are saprophytic on old and dead 

 wood. The hymenia are formed on 

 the surface of the gelatinous mass. The 

 basids vary in appearance, and are usually 

 provided with fine elongated sterigmata 

 and reniform spores. Certain forms such 

 as Sebacina (Tul.) and Hypochnus (Fr.) 

 do not possess gelatinous membranes. The 

 course of development is much the same 

 as in Exobasidium. The germinating 

 basidiospore gives rise under ordinary con- 

 ditions to the compound sporophore 

 again. Under other conditions, it has been 

 observed m Dacryomyces, the germ-tubes 

 do not grow to any great length, but produce 

 secondary spores, or they form sprout-cells. 



The basidiospores of the same form divide transversely at maturity, usually 

 into four cells, each of which may germinate. It should be added that 

 on germination these secondary spores give rise to myceles. The hyphae 

 of such myceles, moreover, as well as those proceeding from basidiospores, 

 sometimes give rise to tufts of rod-like cells, which in turn produce 

 myceles. Similar phenomena have been observed in other Tremelline-x. 



Fig. 317. — Exidia spiculosa Sommerf. 

 Longitudinal section of portion of 

 hymenium (much magnified). jt, 

 spores ; b, basids : //, hyphae of 

 thallus. (After Tulasne.) 



