CLASSIFICATION 499 



X. hypoxylon, is fairly abundant on old stumps and logs ; it usually 

 grows in clusters ; the black, irregularly club-shaped ascophores 

 vary from 2-3 in. in length, and often exceed J in. in thickness 

 near the tip. If in a mature condition, the surface is corrugated 

 or rough, clue to the slightly projecting mouths of the perithecia. 

 If a section is made of one of the clubs, the periphery is seen to be 

 crowded with flask-shaped perithecia ; the substance of the stroma 

 or fleshy, central portion is white and fibrous. A very thin section 

 of the peripheral portion, when examined under a microscope with 

 a magnification of about three hundred diameters, will show the 

 flask-shaped perithecia with the mouth opening outwards to the 

 circumference of the fungus and containing asci, each containing 

 eight dark brown, obliquely elliptical, i-celled spores, arranged in a 

 single row. 



So far we ha\'e been dealing with species of Pyrenomycetes that 

 have numerous perithecia embedded in a more or less fleshy sub- 

 stance, the stroma ; but there are myriads of species where no 

 stroma or sterile portion is present. In such cases the minute 

 perithecia are either collected in groups, but entirely free from each 

 other, or they may be scattered singly. Such species are truly 

 microscopic fungi, and occur as minute black points projecting 

 from dead wood, herbaceous stems, leaves, etc. If the student is 

 desirous of becoming acquainted with this minute but interesting 

 group of fungi, it is only necessary to examine the lowest portion 

 of dead nettle, thistle, or burdock stems, when in ninety-nine 

 times out of a hundred reddish stains will be found, and on closer 

 examination the minute black perithecia will be seen half buried 

 in the stem. Microscopic examination of a thin shce or section 

 taken through the fungus and the matrix it is growing upon will 

 alone reveal the entire structure. 



TUBERACE^ 



The species belonging to this family grow underground, and are 

 consequently almost or entirely unknown to the majority of 

 mycologists, although several of the species are by no means un- 

 common in this country. The different species vary considerably 

 in size, some being not larger than peas, whereas others are as large 

 as a good-sized potato, and, generally speaking, they more or less 

 resemble medium-sized or small potatoes in appearance. Some 

 are globose, others variously warted or lobed ; the wall varies in 

 colour from white, pale brown, rusty olive or blackish, and the 

 surface may be quite smooth, minutely wrinkled or warted, or 

 covered with large pyramidal warts. The entire structure or tuber 

 is termed the ascophorc, and the central jwrtion is the gleha, which 

 often presents a more or less marbled appearance, or resembling a 

 section of a nutmeg ; the paler lines, called dissepiments, which are 

 often much branched and wavy, correspond in structure and func- 



