ASEXUAL REPRODUCTION 103 



have a thin wall, and germinate once, may be mentioned 

 azygospores and chlamydospores. 



Both these become surrounded by a thick cell-wall, and 

 are true resting-spores, that is, they require to remain for 

 some time in a dormant condition before they are capable 

 of germination, yet both are asexual in origin. Azygo- 

 spores are found in some species of the Mucorineae ; 

 they are formed on the same plan as true zygospores, but 

 no fertilisation takes place. Either the two gametes do 

 not come in contact, or only a single gamete is present. 

 These solitary gametes increase in size, develop a thick 

 cell-wall, undergo a period of rest, and germinate after the 

 manner of zygospores. 



Chlamydospores are also thick-walled resting-spores, 

 produced interstitially on vegetative mycelium, in certain 

 Mucorineae and Agarics; rarely on short lateral branches, 

 as in Hypomyces, belonging to the Ascomycetes. 



Sclerotia are the most general of purely vegetative repro- 

 ductive bodies. They consist of more or less globose 



the sexual fruit or perithecia ; 2, perithecia or sexual fruit on a larger scale, 

 showing the papilla at the apex, which is perforated for the escape of the 

 spores ; 3, section of perithecium, showing the wall to consist of two 

 layers ; 4, an ascus containing eight spores, also two paraphyses ; 5, tip 

 of an ascus after treatment with iodine, showing the arrangement for 

 effecting the opening of the ascus, due to expansion of the dark portion, 

 so as to admit of the escape of the spores ; 6, ascospores, one of which is 

 germinating ; 7, brown mycelium with swellings at intervals ; this peculiar 

 swelling just below the septum is very characteristic of two or three allied 

 parisitic species of Rosellinia ; 8, a black sclerotium belonging to the 

 fungus, bursting through the cortex of a root, and bearing several clusters 

 of conidiophores bearing conidia ; 9, a single conidiophore on a larger 

 scale, showing the mode of branching : conidia are borne at the tips of the 

 branchlets ; 10, free conidia ; n, a pycnidium, or second form of conidial 

 fruit, in which the conidia or stylospores are produced in a conceptacle ; 

 12, stylospores. Fig. i, nat. size ; the remainder highly mag. 



