380 DIVISION III. MODE OF LIFE OF THE FUNGI. 



afterwards by Brefeld 1 . Species of Mucor (M. stolonifer and M. racemosus), Penicillium 

 glaucum,Trichothecium roseum, and other species are able to make their way into sound 

 juicy fruits, and vegetate and cause rottenness in them. These do not rot without the 

 Fungi. If spores are sown on the uninjured surface of thick-skinned fruits like the 

 apple and pear, where there is sufficient moisture for germination, the germ-tubes are 

 unable to penetrate into them or do so with difficulty ; but they enter with ease if the 

 spores are sprinkled on wounded places where the skin is broken. Mycelia which have 

 already acquired some strength are better able to force their way through the unbroken 

 skin. The softer the fruits have become from other causes the more easily are they 

 penetrated by the Fungus ; fruits therefore like strawberries and raspberries with thin 

 skins are* very liable to be attacked. Davaine found that the vegetative organs of 

 succulent plants, such as Sempervivum, Mesembryanthemum, and Stapelia show the 

 same phenomena as thick-skinned fruits. Observation of the fruits shows that the 

 Fungi develope more easily the nearer the vital powers of the parts attacked are to 

 their lower limit, and at this point the conditions of saprophytic vegetation make 

 their appearance. 



The parasitic phase of vegetative life is seen in its more characteristic form in 

 many other facultative parasites on plants, and with many shades of difference in 

 different species. The Sclerotinieae, Pythieae, Nectrieae, and Hartig's tree- 

 destroying Hymenomycetes may be taken as examples for closer consideration. 

 Many other Fungi, species of Pleospora and Cladosporium for example and allied 

 forms will have to be added to this if the group is more thoroughly investigated. 



Of the Sclerotinieae, Sclerotinia Sclerotiorum (see pages 30, 52, 218) may go 

 through the whole course of its development as a saprophyte and finds opportunity 

 for this in the natural state on dead plants. But it can also attack certain living and 

 healthy plants and parts of plants as a parasite and destroy them. But according to 

 our present experience it always requires to go through a previous stage of existence 

 as a saprohyte in order to be capable of parasitism. The allied S. ciborioides which 

 preys on clover behaves in a similar manner. 



Sclerotinia Puckeliana inclines more in the direction of saprophytism ; both 

 the mycelia which produce gonidia and those which form sclerotia are found chiefly in 

 dead parts of plants, especially on decaying leaves, &c. At the same time it is one of 

 the chief agents in the production of decay in juicy fruits, and more thorough investi- 

 gation will confirm the experience drawn from every conservatory, that the mycelium 

 when it has once reached a certain degree of strength becomes parasitic on living plants 

 and kills them. 



I have previously 2 given a very imperfect account of the circumstances connected 

 with the vegetation of Peziza Sclerotic-rum, and at that time I also misunderstood to 

 some extent the facts which were stated about it. More recent observations have given 

 me a clearer understanding of the matter and it will be well to describe them here in 

 greater detail. The ripe ascospores germinate in pure water, emitting short tubes which 

 soon cease from further development ; in a suitable nutrient solution, in must of grapes for 

 instance and on ripe juicy berries of any kind, they develope into a vigorous mycelium 

 which forms sclerotia, and the same result is obtained if they are sown on dead vegetable 



1 Sitzgber. d. Naturf. Freunde zu Berlin, Dec. 21, 1875. See Bot. Ztg. 1876, p. 281. 

 3 See the first Edition of this work, p. 215. 



