126 



THE AGRICULTURAL NEWS. 



April 16, 1910. 



FUNGUS NOTES. 



THE CHIEF 



GROUPS 



Part I^■. 



OF FUNGI. 



lANA 



The Ascomycktes. The next group of fungi to be 

 Considered is the Ascomjcetes. These fungi all possess 

 a mycelium which is divided up by transverse walls, and they 

 are characterized by the formation of a sac, or ascus, in which 

 a definite number of spores, usually eight, is borne. The whole 

 group may roughly be divided up into the following sub- 

 groups: — 



Protoascineae. 



Protodiscineae. 



Helvellineae. 



Discomycetes. 



Tuherineae. 



Plectascineae. 



Pj'renomycetes. 

 This division is a more or less rough one, and 

 in fact, there are so many classifications of the 

 Ascomycetes on dift'erent lines that it is a matter 

 of some difficulty to choose between them. 



As has been stated previously, the bulk of the 

 evidence which has accumulated during recent 

 years would tend to show that the asci were origin- 

 ally formed as the outcome of a sexual process. 

 In some genera, an organ correspond to the oogonium 

 of the Oomycetes, and another similar to the antheri- 

 dium in the same group, have been found to exist, 

 and in some cases an actual fertilization process 

 is known to occur. In many genera, however, the ^ , g, ScrFRr 

 process has become obsolete, or modified in one way '.'' ptt^kft 

 or another, so that it differs considerably from its " 



original form. The scope of this article does not 

 permit of a further discussion of thi 

 which is one of very great complexity. 



The rRuTOAsciNEAE and protodiscineae. In these 

 groups, the asci are produced over the whole mycelium, 

 or sometimes from a special part of it, but are not 

 enclosed in a particular form of covering, consequently 

 there is no very definite fruit-body by 

 which the members of the groups can 

 be recognized, as the asci are in most 

 cases borne free on the surface of the 

 host-plant. These fungi often cause 

 various malformations of the host, such 

 as witches' brooms of many trees, especi- 

 ally in the temperate zone, leaf curl, leaf 

 blisters, and malformations of fruits, with 

 which the genera E.ojascus and Tapltrlna 

 are so frequently associated. The asci 

 are usually short and more or less cylin- 

 drical. They are produced from hyphae 

 growing in the outermost wall of the 

 epidermis of the host, known as the 

 cuticle. They grow out at right angles 

 to the surface of the host, bursting the 

 cuticle as they develop. The fungi 

 known as yeasts belong to the first of these groups. 



In all the other members of the Ascomycetes, the asci 

 are borne on definite fructifications, either open when ripe, 

 so that the asci are freely exposed to the air {niMthtcia), or 

 in the form of closed, often spherical, masses, which decay 

 and so liberate the spores (cleistol/iecia), or in boxes with 



at the top ijjerithecia). Both the apothecla and perithecia 

 are often carried on some form of stalk or supporting arrange- 

 ment built up from the hyphae of the fungus, or, in some 

 cases, are borne on, or sunken in, a .special mass of closely 

 woven hyphae known as a stroma. In other cases, the 

 fructifications are originally sunken in the host plant and 

 only break out on the surface when ripe or nearly so. 



The IIELVEILINKAE. In this group, the fructifications 

 are usually erect and fieshy, though they may be of various 

 forms. They are generally lobed, or wrinkled, and bear the 

 asci all over their uj>per surfaces. Some of the species are 

 edible, as for instance, some in the genus Morchella (morel). 

 Others are suspected of being parasites. 



The DISCOMYCETES. This group of fungi is character- 

 ized by having its asci produced in fructifications known as 

 apothecia, mentioned above. The fructifications are more or 

 less cup-shaped when ripe, and either borne on a stalk of 

 sterile interwoven hyphae, or are sessile on the underlying 

 substance (substratum); the asci are borne over the whole of 

 the hollow upper surface, and at right angles to it. Between 

 the asci are numerous free hyphae, often somewhat 

 swollen at the end. These are known as hairs, or 

 paraphyses. The asci and paraphyses often give the 

 inner surface of the cup a smooth or somewhat gelati- 

 nous appearance. When young, the apothecia are 

 closed, and consist of an outer covering layer of 

 closely woven, sterile hyphae, from which the paraphyses 

 spring, and an inner layer of special hyphae from which 

 the asci are produced. The fructifications, when young, 

 may be immersed in the substratum, but become free 

 when ripe, and open out to form the cup-shaped struc- 

 ture already described. The group is further subdivided 

 by the characters of the apothecia — whether immersed 

 in the substratum when young, or free from the start; 

 whether sessile or stalked, black or coloured, and similar 

 points. The spores are usually forcibly extruded 



cjuestion, ^ '■ ^ from the asci by the mutual pressure of the asci and 



paraphyses. They may be of different shapes, from 

 oval to linear, one- or more celled, colourless or coloured, 

 transparent or opaipie; and such characters serve to differ- 

 entiate genera and species. This group does not contain any 

 parasites very well known in the West Indies; Fig. 21 shows 

 the stalked apothecium of Sclerolinia 



Fkj. 22. Myriangium Duriaei. 

 (a) Tissues of Host, (b) Stroma of 

 Fungus, (c) Tissue Producing Asci. 



iiome definite method of opening by means of a lid or a pore 



fuckeliana with the hollow cup at the 

 top. The apothecia have grown out 

 from a hard mass of fungus mycelium 

 known as a sclerotium. 



The TUBERiNEAE. The fructifica- 

 tions are closed, or nearly so, and con 

 sist of a more or less solid mass of tissue, 

 often penetrated by channels in which 

 the asci are produced. The spores are 

 liberated by the rotting of the ascus. 

 The channels in the closed fruits often 

 lead in the direction of a portion of the 

 surface, only covered by a very thin layer 

 of tissue, which breaks down and liber- 

 ates the spores. In some cases, the 

 fructifications are open entirely; in others, 

 very thick layers surround the whole 

 cleistothecium. These characters serve to subdivide the 

 group. The asci are usually only 4-spored, and the spores 

 are often spiny. All the fructifications are borne under 

 ground, some of them being edible and known as trufiles. 

 The PLECTASCINEAE. In this group, the fructification 

 is again a cleistothecium, very minute in size, and consisting 

 of a mass of tissue, in which are hollows where the asci are 



