300 RESEARCHES ON FUNGI 



fill up the gaps in the hymenium which the contraction and collapse 

 of the asci have made and thus they assist in maintaining the 

 mechanical stability of the hymenium as a whole. 



The paraphyses of Aleuria vesiculosa and of the Discomycetes in 

 general function : (1) by forming the framework of the hymenium 

 in the young apothecium and thus preparing a place for the asci ; 

 (2) by protecting the developing asci against mechanical injuries and 

 loss of moisture ; and (3) by supporting the mature asci in fixed 

 positions whilst the spores are being discharged. 



In the Discomycetes in general, the paraphyses, during the early 

 stages of their development, grow straight outwards from the 

 hypothecium (subhymenium) and, when fully grown, they are 

 either straight, e.g. in Ascobolus stercorarius (Fig. 132, p. 276) and 

 Ciliaria scutellata (Fig. 135, p. 284), or are straight below and 

 heliotropically curved at their free ends, e.g. Aleuria vesiculosa 

 (Fig. 140, p. 293). Moreover, when fully grown, they are, as a rule, 

 simple and unbranched or, if branched, the branches are bent 

 forwards so that their long axes are parallel with those of the 

 parent hyphae (Fig. 119, d, p. 245). Furthermore, as a rule, the 

 paraphyses in a hymenium do not anastomose with one another.^ 

 The general straightness, the simplicity of structure, and the 

 separateness of individual paraphyses facilitate mechanically the 

 outward growth of the asci and the taking up by the asci of positions 

 that are advantageous for spore-discharge. The slenderness of 

 paraphyses permits of the paraphyses fitting into and filling up the 

 spaces between the relatively very thick asci, and the club-shaped 

 swellings so characteristic of the apical cells of paraphyses serve to close 

 up the hymenium on its exterior and thus to make it more compact 

 and better adapted for the protection and support of the asci. In 

 some Discomycetes, e.g. Ascobolus magnificus (Fig. 130, p. 272), 

 A. stercorarius (Fig. 132, p. 276), and Rhizina inflata, the outer wall 

 of the end of each paraphysis becomes mucilaginous and the mucilage 

 so produced assists in closing up the exterior of the hymenium. 



^ To this rule I know of only one exception, Sarcoscypha proiracta. In this 

 Discomycete the upper part of each paraphysis is much branched and the branches 

 are packed closely together. I have observed anastomoses between some of the 

 branches {vide supra, p. 244). 



