36 



FUNGI 



of reproduction is needed, and two adjacent hyphse 

 conjugate much as in Spirogyra (see fig. 1, b e, and 

 ALCWE, fig. 4). The resultant zygospore after a 

 period of rest germinates with only a rudimentary 

 mycelium, and immediately reproduces the char- 

 acteristic asexual sporangium. Empusa, of which 

 E. musi-ic is largely fatal to house-Hies in autumn, 

 is the type of the analogous order Entomophthoreae. 

 The Chytridiaceae are an order of minute fungi of 

 which the life-history is fundamentally similar to 

 that of the Protococcaceae among alg.ne. 



The UstilagineiB are a large family, parasitic 

 on phanerogamous plants. Their mycelium rami- 

 fies through the intercellular spaces or the host, and 

 forms also densely- woven masses of spore-bearing 

 hyph;v, which show various degrees of differentia- 

 tion as compound sporophores, so foreshadowing 

 those of higher fungi. These spores produce a 

 short mycelium, of which the branches conjugate 

 in pairs, while the new mycelia thereafter arising 

 re-enter the plant and in time produce new asexual 

 spores. Some are formidable pests of agricul- 

 ture (Ustilago, Tilletia). 



ASCOMYCETES proper. The mycelium is always 

 composed of multicellular hyphae, which in the 

 higher forms interweave into the stroma or thallus, 

 which assumes various characteristic forms and 

 bears the short reproductive hyphae, which in turn 

 bear the spore-mother cells or asci. These are 

 usually tubular, and on reaching full size their 

 protoplasm collects at the top, and the nucleus 



Fig. 2a. Yeast 

 ( Sacchitromyces cerevisice) : 

 A, a, b, c, d, early stages of bud- 

 in^' ; e, later stages; B, starved 

 yeast cell, dividing at a to 

 form four ascospores at b ; c, 

 subsequent germination on 

 return to nutritive fluid. 



Fig. 2 Peziza. 



a, asci, with barren filaments 

 (paraphyses); 6, section of 

 fructification surface ( hi/men- 

 ium); c, preparations for the 

 sexual process which precedes 

 the development of the fun- 

 gus-body; d, fertilisation, with 

 upgrowth of an enveloping 

 tissue, the incipient sporo- 

 carp. 



divides repeatedly, usually producing eight nuclei, 

 which collect protoplasm around them, and, develop- 

 ing cell-walls, become perfect ascospores. In all save 

 a few of the lowest forms ( Eremascus, Exoascus, 

 &c., which are accordingly grouped as Gymnoasci) 

 the fructification is in distinctly developed sporo- 

 carps. In these, besides the ascogenous hyphae 

 with their asci, there is an envelope derived from 

 distinct hyphae of the stroma, which also send in 

 amongst the asci a multitude of barren filaments, 

 the paraphyses. The aggregate of asci and para- 

 physes is termed the hymenium (see fig. 2, a, b). 

 Tulasne and De Bary have shown with tolerable 

 certainty (despite the doubts of Van Tieghem and 

 Brefeld) that the whole fructification arises in 

 consequence of a conjugation of similar hyphse 

 in the lowest forms (Eremascus), or the sexual 

 union of dissimilar ones in higher forms (e.g. 

 Peziza, fig. 2, c, d). 



A brief systematic enumeration of the orders 

 and leading illustrative forms of Ascomycetes will 

 be found of service : 



(1) Gymnoasci. Asci not forming definite sporo- 

 carps with envelope ( Eremascus, Exoascus ). 



(2) Discomycetes (800 species). Sporocarp with 

 envelope, but hynienium completely uncovered, at 

 least at maturity. The most important genus is 

 Peziza, of which the shallow cup-like sporocarp 

 is open from the beginning, though in the allied 

 Ascobolus the envelope encloses the hynienium 

 during development and bursts, scattering the 

 spores. Bulgaria resembles this, but is gelatinous. 

 In Dermatia the cup is leathery or horny. In 

 Stictis the hymenium is almost withdrawn into 

 the stroma, while in Phacidium the sporoearp only 

 breaks out and opens when ripe. In a second 

 but less important family the sporocarps are 

 leathery and black, elliptical, linear, or winding ; 

 of these Hysterias the commonest is PJiytisma 

 acerinum, which forms the large black spots that 

 appear upon almost every leaf of the common 

 maple towards autumn. The Helvellacei represent 

 an opposite tA*pe of development ; the large sporo- 

 carpsare stalled, with club or hat shaped hymenia, 

 open and uncovered by the envelope from the be- 

 ginning. Many are important as esculent, notably 

 the morels (Morchelia esculenta, deliciosa, &c. ), also 

 Helvetia esculenta. The ' mycelium of Rcesleria 

 hypogtra, found on dead and diseased vine-roots, 

 is the ' pourridie de la vigne ' of wine-growers. 



Among the Discomycetes the life-history is often 

 rendered more complex by the mycelium constrict- 

 ing off acrospores from the tips of erect filaments, 

 these acrospores readily reproducing the mycelium. 

 This stage of Peziza fuckeliana was formerly 

 known as Botrytis cinerea; and many other acro- 

 spore-bearing moulds still await similar identifica- 

 tion. Vegetative hyphae also frequently interweave 

 into dense resting masses or sclerotia, as also in 

 the species just named, and those may either re- 

 develop acrospore-bearing hyphae or ( after a winter ) 

 give rise to true hymenial cups. Acrospores, too, 

 may be developed either upon isolated hyphae or in 

 pseudo-hymemal groups, which may be open or 

 flask-shaped (pycnidia). Nor are the many possi- 

 bilities of ' pleomorphic ' variation thus opened up 

 by any means confined to the Discomycetes. 



(3) Pyrenomycetes.T\ns is a large order of small 

 and inconspicuous fungi, in all respects represent- 

 ing a further differentiation of the Discomycete 

 type, primarily in the deepening of the shallow 

 cup-shaped hymenium into a deep flask with minute 

 apical opening (perithecium], but also in a more 

 varied development the most extreme among fungi 

 of pleomorphism or alternation of generations. 

 The number of species is hence very uncertain. 

 Besides the important Ergot ( Claviceps jmrjmrea, 

 see ERGOT ), and its curious ally Cordyceps, which 

 attacks caterpillars, moths, wasps, &c., with its 

 fructification, thus forming the extraordinary 

 ' animal-plants ' and ' vegetating insects ' widen 

 so perplexed the early naturalists, any of the 

 common forms into which the old (and once all- 

 comprehensive) genus Sphaeria has been broken 

 up will serve as type, conveniently Nectria, com- 

 mon in red patches upon dead wood. Some form 

 parasitic patches within lichens. 



(4) Perisporiacew. In these the perithecia are 

 completely closed capsules which fall to pieces on 

 ripening ; there are no paraphyses. The mycelium 

 is thread-like, and acrospores are frequent. Of the 

 100 species some are notable pests, witness Erysiphe 

 and others, commonly grouped as Mildew (q.v.), 

 Oidium Tuckeri, a pestilent vine disease, &c. 

 Easily distinguished by the dark or inconspicuous 

 mycelium are the species of Fumago. To this 

 group also belongs Eurotium, of which the com- 

 mon Bread Mould (E. Aspergillus-glaucus) is a 

 type commonly put before the botanical student, 

 from the comparative facility with which the sexual 



