134 G. MASSEE AND THE FUNGUS FORAY. 



availed themselves of the opportunity may be estimated from the 

 fact that at the present day no fewer than 45,000 species of 

 terrestrial fungi are known, whose distribution is equal to that of 

 the higher forms of vegetable life on the presence of which their 

 existence depends, no fungus having deviated from the primitive 

 parasitic mode of life. 



Fossil wood from rocks belonging to the carboniferous period 

 affords ample evidence of the presence of parasitic fungi belonging 

 to the primitive type indicated above. Neither do the members 

 of the animal kingdom altogether escape, unmistakable evidence 

 of the presence of parasitic fungi in the remains of ancient corals 

 having been recorded ; and even at the present day various species 

 of insects serve as hosts for highly evolved types of fungi. 



In one of the earliest groups of terrestrial fungi, the Perono- 

 sporese, the evolution of a second form of reproduction was 

 perfected, known as the conidial or summer form of fruit. The 

 ancestral sexual fruit produced in the tissues of the host was 

 retained without modification. 



The conidial form of fruit is developed as follows. The members 

 of the Peronosporese are parasitic on living plants, attacking more 

 especially the foliage ; the vegetative mycelium remains inside 

 the host, and after ramifying and accumulating an amount of 

 reserve material, gives origin to immense numbers of specialised 

 branches, which either push through the epidermis or through 

 the stomata into the air, and there produce myriads of conidia 

 or asexually formed, very minute reproductive bodies. 



The object of producing conidia outside the host was for the 

 purpose of utilising the available terrestrial means of spore 

 dissemination. In early times wind and rain would be the dis- 

 persive agents, and with the advent of groups of insects having a 

 taste for nectar or being attracted by brilliant colours, we find 

 groups of fungi, as some of the Ascomycetes — Claviceps, Sclerotinia, 

 etc. — and all the Phalloidete, ottering the attractions of nectar, 

 smell, and brilliant colours in various combinations, for the 

 purpose of eftecting through the unconscious agency of insects, 

 the difiusion of conidia. 



The conidial phase of reproduction in most fungi corresponds 

 to what are popularly known as moulds and mildews, and all such 

 were at one time considered as distinct species, «ach having its 

 own generic and specific name. 



