484 BRITISH FUNGI 



Certain species are large and snowy, but the great majority are 

 minute, and come under the definition of microscopic fungi. As in 

 the Basidiomycetes, there is in the Ascomycetes a family of 

 subterranean fungi, the Tuberaceae, which includes the true truffles 

 and their allies. Numerous species, more especially the microscopic 

 ones, are parasitic, and in many instances prove very destructive 

 to cultivated plants. Among such are the species causing apple 

 scab, potato disease, American gooseberry mildew, etc. Com- 

 paratively very few are edible, those best known in this country 

 are the morels and their allies, large, fleshy fungi, appearirg in the 

 spring or early summer. None are known to be distinctly poisonous 

 but the fungus called ergot, and some few others. 



Key to the Sub-Orders 

 Hymenium or ascus-producing portion of the fungus fully exposed 

 at maturity. General texture fleshy and soft ; hymenium often 

 brightly coloured. DiscomycetacecB. 



!. Hymenium permanently enclosed_^in a] hollow ascophore or 

 perithecium, the spores escaping at maturity through a small 

 opening or mouth. Consistency often hard or carbonaceous. Most 

 frequently black, in some instances brightly coloured. 



Pyy enomy educe ce. 



Sub-Order Discomycetace^ 

 In the Discomycetes the ascophore or entire fungus is typically 

 cup-shaped, either sessile or supported on a stem of greater or less 

 length. In the earliest stage the ascophore is usually globose, and as 

 growth proceeds the upper portion gradually expands, first forming 

 a cup-shaped structure, and finally shallowiy saucer-shaped, with 

 the extreme edge turned up. In some genera the expansion takes 

 place until the upper surface is quite plane, or even slightly convex, 

 without any trace of an upturned margin. The hymenium consists 

 of myriads of asci, packed closely side by side, their upper or free 

 ends forming the surface of the disc or inside of the cup. When 

 mature, the spores escape through an opening formed at the apex 

 or free end of each ascus. Mixed \\ith the asci are numerous para- 

 physes, or slender threads not containing spores ; these are usually 

 the same length as the asci, and their tips, along \\ith the tips of 

 the asci, form the' surface of the hymenium. As a rule the tips of 

 the paraphyses are swollen or club-shaped, and usually contain 

 some colouring matter, which gives the colour to the disc or hy- 

 menium of the fungus. The colour of the hymenium is invariably 

 due to the colour present in the tips of the paraphyses, and is often 

 very bright, crimson, orange, yellow, green, etc. Some species are 

 quite large, but the majority are small, or even minute, yet, when 

 seen under a good pocket lens, or under a low power of the micro- 

 scope, are certainly the most beautiful of fungi. 



