108 MESOMYCETES. 



plasm in the oogonium is formed into one or more oospheres, 

 without any surrounding " periplasm." The oospheres may not 

 be fertilised (p. 100), and then develope parfchenogenetically. 



Genera : Saprolegnia, whose swarmspores disperse immediately after having 

 left the sporangium. S. ferax is the cause of a disease in fish ("Salmon 

 disease ") and in the crayfish. Achlya, whose swarmspores accumulate in a 

 hollow ball before the mouth of the sporangium. Leptomitus has strongly in- 

 dented hyphae, causing a " linked " appearance. L. lacteus is frequent in the 

 waste matter from sugar factories. Monoblepharis deviates from the others by 

 the greater development of its fertilising process ; the oosphere, situated in an 

 open oogonium, becoming fertilised by self-motile spermatozoids, which are 

 provided with a cilium at the posterior end. 



Class 2. Mesomycetes. 



The Mesomycetes are intermediate forms between the Phy- 

 comycetes and the Higher Fungi. In the vegetative organs, and in 

 the multicellular hyphae, they resemble the Higher Fungi; the 

 methods of reproduction, however, show the characters of the Phy- 

 comycetes, namely sporangia and conidiophores of varying size 

 and with varying number of spores ; definite and typically formed 

 asci and basidia are not present. Sexual reproduction is wanting. 

 The HEMIASCI are transitional between the Phycomycetes and the 

 Ascomycetes, the HEMIBASIDII (Brand-Fungi) form the transition 

 to the Basidiomycetes. 



Sub-Class 1. Hemiasci. 



The Hemiasci are Fungi with sporangia which, although resem- 

 bling asci, yet have not, however, a definite form and a definite 

 number of spores. Besides endospores, conidia, chlamydospores 

 and oidia are found. 



Order 1. Ascoideaceae. Ascoidea rubescens forms irregular, reddish-brown 

 masses in the sap issuing from felled Beeches. It has free sporangia, which 

 resemble asci in their structure, in the development and ejection, and in the 

 definite shape and size of the spores. The formation of the sporaugia takes 

 place when the nutriment is nearly exhausted, and resembles that of the conidia, 

 since they are developed from the end of a hypha which enlarges, and the swelling 

 becomes separated by a transverse wall. Within the sporangia numerous spores of 

 a cap-like form are developed, which are set free through an opening at the apex. 

 Sporangia are formed successively at the apex of the same hypha, the second 

 commencing to develope as the first is dehiscing. Conidia and sporangia are not 

 formed simultaneously ; the former may be considered as closed sporangia. 



Order 2. Protomycetaceae. Protomyces pacJiydcrmus causes hard swellings 

 on the stems a ad leaf -stalks of the Cichoriese (Taraxacum, etc.). These swell- 



