226 CLASS ASCOMYCETEAE 



parasitic on twigs of the Southern Beech (Nothofagus), there is formed a 

 fleshy stroma several centimeters in diameter in whose outer half or more 

 the small apothecia arise. These are at first closed but at maturity open 

 at the surface of the stroma. 



A noticeable feature of the larger apothecia of the whole order is the 

 simultaneous discharge of ascospores over a large portion of the hy- 

 menium. This is visible as a cloud, like smoke or steam. This discharge is 

 often accompanied by a hissing sound, as has been verified by the author. 

 The distance to which the spores may be discharged is remarkable, some- 

 times several centimeters. Falck (1916, 1923) has shown that the dis- 

 charge of ascospores is dependent to a considerable degree upon changes 

 in temperature or illumination or upon contact of some other object with 

 the apothecia. Even the stimulus of a gentle current of air is sufficient 

 to cause spore discharge in some species. Buller (1934) gave an extended 

 discussion of the conditions that induce this simultaneous discharge of 

 spores and that affect its direction. In species of Ascobolus and some other 

 genera the ascus at maturity becomes greatly elongated and distended 

 laterally by the absorption of a large amount of water. When the oper- 

 culum gives way the greatly enlarged ascus contracts with much violence 

 and the contained liquid and ascospores are ejected to an amazing dis- 

 tance. In Saccobolus the ascospores are massed together in a ball which 

 is expelled further than would be possible for separate spores. 



It has been shown that differentiation into two distinct sexual strains 

 occurs among some species of this order. Thus Miss Green (1931) showed 

 for Ascobolus furfuraceus Fr. and Betts (1926) for A. carbonarius Karst. 

 that they will not produce apothecia when grown in culture from a single 

 ascospore but require the meeting of mj^'celia developed from different 

 ascospores and then not from any two but from two of opposite sexual 

 strains. On the other hand some species of Ascobolus are fertile when 

 grown from but a single ascospore. This is a phase of investigation that 

 has attracted the attention of students but much still remains to be 

 learned. Drayton demonstrated that in Stromatinia gladioli there are 

 formed on the mycelium arising from one ascospore minute cells (micro- 

 conidia or sperms) and certain receptive structures within which are 

 developed ascogonia with long trichogynes. Such a mycelium remains 

 without producing apothecia. The mycefia produced by the eight asco- 

 spores of the ascus represent two phases, four of each. The sperms of any 

 mycelium of one phase can fertilize the receptive bodies of any mycelium 

 of the other phase and vice versa. Apparently this is not true hetero- 

 thallism or condition of malencss and femaleness of the different strains 

 such as occurs among the Mucorales. It is comparable to the self-sterility 

 of many flowering plants to their own pollen. For example the Bartlett 

 pear pistil rarely develops to a fruit when pollenized by pollen from the 



