Exflanation of Plates. 



[To face PI :tf I. ] 



MYCELIUM. 



{a, b. after Plowright ; c, after Fischer von Waldheini.) 



a. Ustilaj) nvswM .. Hypha from axis of inflorescence of Avena elatior .. 



b. .. ,- • • Hypha gelatinized from same plant 



c. Tilletia striaeformis . . Hypha from leaf with large vacuoles and showing 



dou'ole contour in walls 



xoOO 



x500 



x900 



d. Ustilago olivacea 



e. Ustilago zene 



f. TJstilffjo violacea 



g. Tilletia levis 

 h 



I. Ustilnrjo violacea 

 m. ,. ,, 



p. Usfiliigo iiia;jdis 



q. 



r. Ustilago scahiosa 



SPORE FORMATION. 



{d, after Brefeld*; e-k, after Fischer von Waldheim.) 



Spore-bearing hypha, the swellings indicating the 



formation of spores . . . . . . . . x 400 



. . Gelatinized hypha showing the contents hreaking 



up for spore formation . . . . . . x 900 



Coalesced gelatinous hyphae in which spore formation 



is taking place, and contour of spores distinctly 



visible .. .. .. .. .'. x900 



Spore-forming hypha with commencement of ])ranches 



ending in spores . . . . . . . . x 900 



Young spore still connected with hypha . . . . x 900 



Young spores in various stages of development . . x 500 

 Separation of hypha into two branches with spore 



at end of each of different degrees of ripeness . . x 500 

 . . Spore with shrivelled remains of spore-forming hypha x 500 



SPORE GERMINATION. 



{l-o, and r-s, after Harper; p, q, after Istvanffi.) 



. . Germinating spore with nucleus . . . . x about 1500 



. . Geriuinating spore after first nuclear division, one 

 nucleus remaining in spore, the other wandering 

 into germ-tube . . . . . . x about 1 500 



Promycelium, with two daughter nuclei and a septum 



between . . . . . . . . x about 1500 



. . Conidium budding like yeast . . . . x about 1500 



Germinating spore with single nucleus in promy- 

 celium . . . . . . . . . . X 950 



Four-celled promycelium and conidia with a nucleus 



in each . . . . . . . . . . x 950 



. . Promycelium with four resting nuclei . . x about 1500 



Four-celled promycelium and conidia with a nucleus 

 in each . . . . . . . . x about 1500 



* The magnification of Brefekl's figures is generally too high, probably arii^ing from the mode of 

 reproducing them. 



