ANATOMY OF FUNGI 29 



hence fungus tissues are spoken of as false tissues. In 

 many instances, as in the stipes of Agarics, the inter- 

 weaving of the hyphae is very evident in a section, the 

 general texture is loose, and there are numerous air-spaces. 

 In other cases the tissue is hard and compact, and without 

 air-spaces, as in sclerotia, the cuticle of the pileus in some 

 species of Polyporus^ etc. Elsewhere as in the perithecia or 

 fruits of the Sphaeriaceae, and the tissue of the sporophore 

 of some of the Discomycetes, thin sections cut in whatever 

 direction show isodiametric cells resembling true parenchy- 

 matous tissue, but when such structures are examined in 

 a very early stage of development, their origin from 

 independent hyphae is obvious. 



The tissues of fungi are grouped as follows by Istvanffi : 



1. Merismatic System.- Tissues corresponding to the 

 meristem of higher plants are rarely clearly differentiated. 

 The tips of many rhizomorphs bear a resemblance to the 

 tips of true roots, the mucilaginous sheath in the rhizo- 

 morph of Agaricus melleus corresponding to the root-cap. 

 Zones of growth are also present in the pileus of Agaricus, 

 Polyporus, Stereum^ etc. 



2. Protective System. Under this heading come the 

 various forms of cuticle, in some Agarics consisting of a 

 layer formed of more or less parallel hyphae, which are 

 sometimes cemented together by a substance derived from 

 the deliquescence of the outer layer of the hyphal walls ; 

 in other instances, as in various species of Polyporus, the 

 cuticle becomes pseudoparenchymatous and exceedingly 

 hard. Cystidia, when mineralised, prevent the spores from 

 being removed by slugs, snails, etc. Thick coat of oospores 

 and various resting-spores. Mechanical arrangements for 

 retaining the general form of the fungus consist in the 



