274 PART 111. THE CLASSIFICATION OF PLANTS. 



ductive organs form compact masses of tissue of a somewhat 

 parenchymatous appearance, in which there is no differentiation of 

 tissue-systems, but the superficial layers of hyphae form a kind of 

 tegumentary tissue, termed generally cortex. Considerable differ- 

 ences in the nature of the cell- wall may obtain in different parts of 

 such organs, some walls being soft and mucilaginous, whilst others 

 are relatively hard without, however, ever being lignified. Tn 

 a few Mushrooms (e.g. Lactarius) some of the hyphae form a 

 system of laticiferous tissue, and in others glandular structures 

 occur. 



Except in the simplest forms, the body is generally more or less 

 clearly differentiated into root and shoot. These members can be 

 distinguished partly by their relative position, the root-hyphae 

 growing into the substratum, and the shoot-hyphse into the aii* ; 

 and partly by the fact that the shoot-hyphae bear the reproductive 

 organs. Some parasitic forms have root-like organs, termed 

 ftaustoria, which penetrate into the cells of the host; similar 

 organs occur in some saprophytes, and in others (e.g. crustaceous 

 Lichens) the roots (sometimes called rhizines) consist of bundles of 

 hyphae. There is in no case any differentiation of the shoot into 

 stem and leaf. 



The foregoing account does not apply to the body of the Myxoraycetes, 

 which consists of a multinucleate mass of protoplasm, termed a plasmodium, 

 without any cell- wall. It is formed by the cohesion of a number of small, 

 originally independent cells, like that of the Hydrodictyaceae among the Algae 

 (see p. 242). 



Vegetative propagation is common among the Fungi. The 

 simplest form of it is simple cell-division (e.g. Schizomycetes), or 

 that form of cell-division known as budding or sprouting (gemm- 

 ation) (e.g. the Yeast-forms of various Fungi). It is effected in some 

 cases (e.g. in some Zygomycetes, Ascomycetes, and Basidiomycetes) 

 by unicellular gemmce of various sizes (termed chlamydogonidia 

 when they are relatively large and thick- walled, and are adapted for 

 a period of quiescence ; oidium-cells, when they are small and thin- 

 walled and capable of immediate germination) which are formed 

 by the segmentation of a hypha by transverse septa into short cells 

 which become somewhat rounded and separate from each other ; 

 on germination, each may give rise to a mycelium. In other 

 cases (e.g. many Ascomycetes, such as the Sclerotinieae, Pezizeae, 

 Claviceps, etc. ; some Basidiomycetes, such as Coprinus stercorarius, 



