FUNGI. 93 



intervals (successive), when only one spore at a time is thrown out. 

 The first of these methods is the most frequent, and is brought 

 about by the ascus being lined with a layer of protoplasm, which 

 absorbs water to such a degree that the elastic walls are extended 

 at times to double their original size. The spores are forced up 

 against the free end of the ascus, a circular rupture is made at 

 this point, and the elastic walls contract, so that the fluid with 

 the spores is ejected. Special means may in some instances be 

 found to keep the spores together, and compel their simultaneous 

 ejection. Thus, a tough slime may surround all the spores (Suc- 

 cobolus), or a chain-apparatus, similarly formed of tough slime ; 

 or there may be a hooked appendage from each end of the spores 

 which hooks into the appendage of the next spore (Sordaria). The 

 paraphyses occurring between the asci in many Ascomycetes, also 

 play a part in the distribution of the spores, by reason of the 

 pressure they exercise. The asci in some of the Pyrenomycetes, 

 which are provided with jar-shaped fruit-bodies, elongate to such 

 an extent that, without becoming detached from their bases, they 

 reach the mouth of the fruit-body one at a time, burst and disperse 

 their spores, and so make room for those succeeding. An ejection 

 of the spores at intervals from the ascus is rarer. It takes place, 

 for instance, in Pleospora, whose asci have a double wall. The 

 external wall, by absorption of water, at last becomes ruptured, 

 and the internal and more elastic membrane forces itself out in 

 the course of a few seconds to one of two or three times greater 



, O 



length and thickness, so that one spore after another is forcibly 

 ejected from a narrow aperture at the end of the ascus. 



Germination of spores (conidia and chlamydospores). In 

 many spores may be found one or more germ-pores, i.e. thinner 

 places, either in the inner membrane (uredospores, Sordaria) 

 or in the external membrane (teleutospores in Rust-Fungi), 

 through which the germination takes place. Generally this does 

 not occur till the spores have been set free : in some Ascomycetes 

 germination commences inside the ascus (Taphrina, Sclerotitiia ) . 

 The different ways in which the spores germinate may be classified 

 into three groups. 



I. THE ORDINARY GERMINATION occurs by the spore emitting a 

 germ-tube, which immediately developes into a mycelium. In 

 spores with a double wall it is only the inner membrane which 

 forms the germ-tube. In swarmspores a single wall is formed 

 after the withdrawal of the cilia, and this, by direct elongation, 



