CRYPTOGAMS 



385 



are subject to variation. The sporangia of the genus Thamnidium are, on the other 

 hand, regularly dimorphic, and a large sporangium containing many spores is formed 

 at the end of the main axis of the sporangiophore, while numerous small sporangia, 

 having but few spores (sporangioles), are produced by its verticillately branching 

 lateral axes. The sporangia may at times develop only a single spore, as the 

 result of certain conditions of food-supply, and in this way assume the character 



of conidia. This dimorphism is 

 even more complete in the trop- 

 ical genus Choanephora. In this 

 case, in addition to large spor- 

 angia, conidia are produced on 

 special conidiophores. There are, 

 finally, Zygomycetes (e.g. Chaeto- 

 cladium) whose only asexual 

 spores are conidia. In this one 

 group, therefore, all transitional 

 forms, from many-spored spor- 

 angia to unicellular conidia, are 

 represented. 



Flo. 3'25. Mm-oi- Mucrdo. Different .stages in the 

 formation and germination of the xyj^^pore. 

 1, Two conjugating branches in contact; ,.'. 

 septation <>f tlic conjugating cells () from the 

 siispeiiM>r> (//) ; J, more advanced sta.^e. th. 

 conjugating cells (a) are still distinct from one 

 another : the warty thickenings of their walls 

 have commenced to form ; it, ripe xygospore (//) 

 between tln j snspeiisors (a)', '>. germinating: 

 xygospore with a p j rm-tnlie bearing a spor- 

 angium. (After BREFELD, 1-4 x 2'25, "> x circa 

 60, from v. TAVKI., /'//:..) 



FIG. 32(i. Empusti Mvrai: A, Hypha 

 from the body of a fly. Ji, Young 

 conidiophore arising from the my- 

 celium and projecting from the 

 body of the insect. C, Formation 

 of the conidimn into which the 

 numerous nuclei have passed from 

 the conidiophore. (After OLIVE, 

 x 540.) 



2. The Entomophthorineae ( 57 ) is a small group of Fungi which mostly In v 

 parasitically in the bodies of insects and caterpillars. The multinucleate mycelium 

 remains non-septate or later becomes divided into cells. Asexual multiplication is 

 effected by means of conidia which contain one or numerous nuclei. These arix; 

 singly at the ends of branches of the mycelium and when ripe are forcibly abjected. 

 Sexual reproduction is by means of zygospores, in place of which azygospores 

 frequently urisc. 



2 c 



