136 ASCOMYCETES. 



Urcdincac, we designate amongst the Ascomycctcs, as asci, and 

 amongst the Protomycdcs and Basidiomycetes as basidia. This cell, 

 a honiologue of the primary embryo-cell of the Archegoniatae 

 and Emhvyonatac, indicates a turning-point in the development, 

 the beginning of a new generation. It either becomes a resting- 

 spore, as in Phycomycetes, Ustilayincac, Urcdincae (exclusive of 

 Coleospormm and Chrysomyxa), or divides at once to form free 

 endospores as in the Ascomycetes, and exospores in the Protomycetes 

 and Basidiomycetes. From these facts the distinction between 

 basidiospores and conidia, asci and sporangia, teleutospores and 

 chlamydospores, has been for the first time distinctly proved." 



ASCOMYCETES. 



The Ascomycetes show relationship to the higher fungi in the 

 possession of a septate mycelium. Their spores are produced in 

 cylindrical sacs called asci, wdience the name Ascomycetes is 

 given to the group. 



The primary nucleus of each ascus results from the copulation 

 of two nuclei of distinct origin and with no relationship to each 

 other. From the division of this nucleus and its daughter- 

 nuclei, there are produced a number of free endospores varying 

 according to the species. These may remain unicellular or, by 

 means of septa, become many-celled bodies from each of whose 

 individual cells germ-tubes may develop. It is advisable to give 

 the name spore to each cell-group which develops from one 

 nucleus.^ 



Ascospores are never zoospores, but are always quiescent and 

 possess a cell-membrane. They are generally forcibly expelled 

 from the asci. The asci originate either directly from the my- 

 celium, as in the Saccharomycetes and some Exoasceae,- or a part 

 of the mycelium becomes differentiated into an ascogenous layer. 

 The ascogenous layer may include only a few cells, as in the 

 lower forms, or it may be a complex tissue. In the higher forms 

 the aggregations of asci are enclosed in coverings, but the asco- 

 genous layer takes no part in the formation of the enclosures 

 nor of the accessory organs known as paraphyses and periphyses. 



1 De Bary held that each individual cell capable of germination is a spore, the 

 single niidti-celhdar spores he designated sporidesmia. 



-Hansen, Centrcdhl. f. Bacterioloijie mid ParaHitenkunde, 1893. 

 Sadebeck, Die parasitischen Exoasceen, 1893. 



