IjO 



DIVISION II. — COURSE OF DEVELOPMENT OF FUNGI. 



simple cases after conjugation from each suspensor near their line of junction with 

 the ripening zygospore ; these branches, which have stout dark-coloured walls, 

 complete their growth as the zygospore ripens and form a loose envelope round it. 

 In Phycomyces ! the branches of the envelope divide dichotomously and their 

 ramifications spread in every direction; in Absidia 2 they either do not branch again 

 or they have short tooth-like lateral branches, and bend crosier-wise from the two 

 suspensors over the zygospore. The formation of the envelope is more complicated 

 in Mortierella, in which the ripe zygospore is encapsuled by a number of layers 

 of compactly woven hyphae. The accounts which we possess show that the 

 development of the envelope varies in the different species. In M. nigrescens 3 the 

 hyphae of the enveloping tuft grow out at first after conjugation from the suspensors 

 and later also from the filaments bearing them, and enclose the zygospore as it 

 ripens in their copious ramifications. In M. Rostafinskii 4 the hyphae do not spring 

 from the suspensors, but only from the point of origin of the adjacent mycelial 

 hyphae, and envelope the conjugating pair with their branches before conjugation 

 is effected. 



Azygospores. It happens not unfrequently in the Mucoreae that zygospores 

 which are otherwise normally developed contract a permanent constriction at the 

 place of coalescence, and the coalescence is therefore to outward appearance less 

 perfect than it usually is. But it may also happen that the gametes in a pair, after 

 being formed in the normal manner, do not coalesce, do not even come into contact 

 with one another, and the gametes may even make their appearance singly and not 

 in pairs (Absidia, Mucor tenuis), and yet have the normal structure of zygospores 

 and their normal capacity of germination. Spores thus formed and resembling 

 zygospores have been named azygospores. They are not produced in all species ; 

 they have not been found, for instance, after long continued search, in Mucor 

 stolonifer or in Chaetocladium ; they have been found in Absidia septata, A. 

 capillata 6 , Mucor fusiger 6 , and most frequently in Sporodinia. In this species they 

 are associated with the zygospores. Mucor tenuis according to Bainier only forms 

 azygospores, and perhaps Fries' Azygites 7 , a plant which requires more precise 

 investigation, is also one of the Mucorini which have this peculiarity. 



Zygospores or azygospores have up to the present time been described in Sporodinia 

 grandis ; Mucor Mucedo, M. racemosus, M. tenuis (Bainier), M. fusiger, M. stolonifer ; 

 Pilobolus (Pilaira) anomalus (Brefeld, Van Tieghem) ; Phycomyces nitens, Ph. micro- 

 sporus (V. Tieghem) ; Absidia capillata, A. septata (V. Tieghem ) ; Mortierella 2 species 

 (vid. sup.) ; Choanephora I spec. ; Chaetocladium Jonesii and Ch. Fresenii (brefeld) ; 

 Piptocephalis Freseniana I Br.) ; Syncephalis Cornu (V. Tieghem), S. nodosa, S. curvata 

 (Bainier ) ; altogether 19 species, very lew compared with the large number of existing 

 species. In many they may have been overlooked, being rare and concealed in the 

 substratum, and may yet be found. In others, as Pilobolus crystallinus, P. oedipus, 

 and Thamnidium elegans, they have been so often sought for in vain that it may be 

 assumed that they never occur. 



1 Van Tieghem, I, t. 20. 



2 Id., Ill, t. 11. 



3 Id. III. 



4 Brefeld, Schimmelpilze, IV. t. V. 



Van Tieghem, III. 



6 Id. II, p. 73- 



7 See Tulasne, Sel. Fung. Carpol. I, p. 64. 



