lOO 



MORPHOLOGY AND LIFE-HISTORY OF YEASTS. 



that here the asci are produced by a special organ, to which the 

 name ascogone has been given. This is a unicellular or poly- 

 cellvdar organ springing from the mycelium and putting forth 

 the asci either direct or'upon branched processes. At the same 

 time it surrounds itself with an envelope, of one or several layers, 

 thus broadly completing the formation of the carpoascus. The 

 shape of the envelope and therefore of the entire carpoascus, 

 forms the principal characteristic on which the sub-class of the 

 Garpoascece are allotted their position in the botanical system. 

 When the envelope does not enclose the ascogone on all sides, 

 but merely serves as a support therefor (or for the asci) on the 

 basal side, leaving the others free, then a disc-like or cup-shaped 

 fruit is formed, which is called an apothecium. Ascomycete^ 

 producing fruit of this kind are termed Discomycetes. If, on 

 the other hand, the ascogones or asci remain surrounded on all 

 sides by the envelope when ripe, then the fruit is termed a 

 perithecium, i.e. globular, oval, or in the foi^m of a short bottle ; 

 and the Ascomycetes producing same are classed along with the 

 order of Pyre7iomycefes, or nuclear funcji, the second of the 

 two orders into which the sub-class of Carpoascece has been 



divided. 



If the perithecium is of a kind that exhibits no aperture at 

 all during the whole period of its existence, so that the contained 

 asci or ascospores cannot escape into the open air unless the 

 perithecial membrane breaks up or is destroyed, then the peri- 

 thecium is termed cleistocarpous or enclosed. All the Pyre- 

 nomycetes bearing fruit of this character are included m the 

 sub-order of Perisporiacece. The common greenish-blue bread 

 mould belongs hereto. 



On the other hand, when the perithecium is of such a type 

 that, in the ripening process, it develops an orifice through which 

 the asci or ascospores are able to escape, it is then said to be 

 peronocarpous. The second sub-order of the Pyrenomycetee 

 exhibits this kind of fruit, and is called Sphceriace(B. 



Scheme of subdivision of the Ascomycetes Class. 



Ascomycetes 



(Mycomycetes 

 with endogen- 

 ous spores) 



'(a) Asci naked 

 (b) Asci with 

 envelope 

 (Carpoas- 

 cus) Car- 

 poascecc 



Gymnoascece 



(a) Carpoascus 

 is a peri- 

 thecium : 

 Pyrenomy- 

 cetes 



1. Perithecium 



cleis t o - 

 carpous . 



2. Perithecium 



pe r o n 0- 

 carpous . 



Perisporia- 

 cece. 



(j3) Carpoascus 

 is an apo- 

 thecium D 



Sphceriacece. 



i s'c m y- 

 cetes. 



