468 SYSTEMATIC BOTANY. 



to force their way out and form asci, in each of which there are 8 aso.o- 

 spores. These spores germinate and produce a mycelium, which again bears 

 conidia. The sclerotia also when kept so long that the ascogenous 

 threads have lost the power of forming asci, germinate and form the 

 usual conidia. The sclerotia are in structure so similar to the well- 

 known fruits of the Tuberacece (Truffles), that, however, strong the 

 resemblance of the sexual organs may be to those of Eurotium, they 

 must be classed with the former. In no other species of Tuberacece have 

 conidia been observed. 



Suborder 4. PYRENOMYCETES. Fungi growing usually on dead 

 organic bodies and on living plants, and forming round or flask- 

 shaped conceptacles (perithecia) with walls of pseudo-parenchyme, 

 and containing long club-shaped asci, each of which produces (as 

 a rule) 8 spores. The perithecium is in some cases open at first, 

 but in others an opening is ultimately formed in the neck of the 

 flask, through which the spores are emitted. (It is not yet clear 

 whether this fructification be generally the result of sexuality or 

 not.) When the ascospores germinate, they produce a mycelium 

 on which are formed conidia, stylospores (in pycnidia), and sperm- 

 atia (in spermogonia). In many species one or more of these 

 organs are wanting, and in many others one or more of these are 

 present and the perithecia wanting. Illustrative Genera : Clavi- 

 ceps, Tul. ; Nectria, Tod. ; Spliceria, Hall ; Xylaria, Hill ; Dichcena, 

 Fr. ; Venturia, Er. ; Stiymatea, M. 



Structure, &c. In a number of species (e. g. the Sph&ria siniplices) the 

 perithecia arise on a very fine mycelium, singly or in groups, and in such 

 cases it seems to be probable (from Woronin's observations) that they are 

 the result of a sexual act. In other cases, however (as in Xylaria), the 

 perithecia are formed on large club- or basin-shaped stromata, consisting 

 of dense masses of tissue. It is uncertain whether the stroma be merely 

 a receptacle, or whether there takes place in it a sexual act which gives 

 rise to the perithecia. The conidia are formed not only on the mycelium, 

 but also on the stroma or even (as was seen to be the case in PeniciUiian) 

 on the wall of the perithecium. Sometimes conidia and slylospores of 

 two different forms occur in the same species. It has been suggested that 

 the spermogonia and pycnidia are merely parasitic on the Pyrenomycetes j 

 but this view has, in the case of the pycnidia, been recently disproved by 

 the researches of Dr. Bauke, and in the case of the spermogonia by M, 

 Cornu, who was the first to cause the spermatia to germinate and repro- 

 duce the mycelium. This Suborder, like the Discomycetes, includes a 

 great number of forms, many of which seem to be only stages in the life- 

 history of other plants, and which have received the names of distinct 

 genera and species. 



Suborder 5. LICHENES (figs. 516 & 517). Fungi consisting of a 

 thallus of densely interwoven hyphae, sometimes forming pseudo- 

 parenchyme, deriving their nourishment from minute Algae 



