350 DIVISION III. MODE OF LIFE OF THE FUNGI. 



Fungi which are in the habit of germinating in the digestive canal of warm- 

 blooded animals, the Mucorini, Piloboli, Ascoboli, and indeed also the Sordarieae 

 and Coprini, have an optimum corresponding, as might be expected, with the 

 temperature of the body of the animal. Brefeld : even gives the minimum as from 35 

 to 40 C. in the case of one species of this group, which he does not determine 

 more nearly. He also gives from 35 to 40 C. as the minimum in the case of Cru- 

 cibulum vulgare, which is supposed to germinate regularly in the intestines of animals, 

 while Eidam 2 has observed its germination at a temperature between 20 and 25 C. 



The supply of oxygen, which must be regarded as necessary for general reasons, 

 has never been specially investigated in the germination of the Fungi. Its necessity 

 is shown when spores are sown in drops of liquid beneath a covering glass. The 

 spores germinate better the nearer they lie to the edge of the covering glass where 

 there is a free supply of air ; they often do not germinate at all in the middle. 



The necessity of a supply of water is evident in all cases and is intelligible. 

 It is plain from the swelling of the germinating spore and the formation of successively 

 growing vacuoles that the process of germination begins with absorption of water. It 

 depends on the species or the form of the spore whether pure water is necessary, or 

 whether the water must contain certain nutrient substances or whether germination 

 takes place both in water and in nutrient solutions. 



The first category includes a number of strictly parasitic forms, the Perono- 

 sporeae especially and Uredineae, and also the Erysipheae, Polystigma rubrum and 

 species of Rhytisma. Many of the Lichen-fungi may also belong to it, but this is a 

 point which requires investigation. The spores especially of the two first groups 

 germinate best when they are not in but on drops of water or in an atmosphere 

 saturated with vapour, which no doubt supplies them with the requisite amount of 

 water in the shape of slight precipitations. Nutrient solutions may even hinder 

 germination. Observation shows that the normal processes in germination are 

 effected entirely at the expense and by the transference of the substances in the spore 

 (see sections LXXIX LXXXII). 



The gonidia of Mucor stolonifer, Chaetocladium and most of the Mucorini 

 and the ascospores of Sclerotinia Fuckeliana are examples of the third category which 

 represents the other extreme. These Fungi emit at best only weak rudimentary 

 germ-tubes in pure water, and it is not certain that these are not due to small 

 admixtures of nutrient substances which entered the water with the spores. The 

 ascospores of the Sordarieae and the spores of the Coprini also belong to this list. 

 Their germ-tubes have been obtained hitherto only in nutrient solutions, and we have 

 no exact account of their behaviour in pure water, because it has but little practical 

 interest. 



The spores of most Fungi belong to the second and intermediate category, with 

 an inclination to one or other extreme according to the species. Examples are seen in 

 the gonidia of Penicillium, Sclerolinia Fuckeliana, and other common forms of Moulds, 

 and in the spores of the Ustilagineae and Tremellineae, with respect to which the 

 reader should compare the statements in the sections of Chap. V which refer to them. 



1 Schimmelpilze, IV, p. 20. 



2 In Cohn's Beitr. z. Biol. II. 



