2od Urocystis — Doassamia. 



Sooner or later the coiiidia, while still attached, begin to germinate at their 

 free end, by putting forth a slender germ-tube, only about half the breadth 

 of the conidium, and this grows ou^t to a varying length, according to the 

 supply of nutriment. It is filled with dense protoplasmic contents, more 

 particularly towards the tip. These slender delicate threads, when they 

 grow out to any considerable length, show an irregular curving, and represent 

 the infection-threads which penetrate the young seedling, if they reach it 

 at the proper stage of groAvth. 



(Plates IV., v., VI., VII., LI.) 



DOASSANSIA Cornu. 



This genus stands higher than all the preceding in its morphological dif- 

 ferentiation. The Peridium formed by the sterile envelope of cells which 

 encloses the fertile spore-cluster is characteristic of the genus, and places it 

 at the top of all knoAvn Tilletiaceae. Since the hosts are either water or bog- 

 plants, the cortex of sterile parenchymatous cells filled with air, is evidently 

 a contrivance to enable the spores to float, or be surrounded by water until 

 they escape and germinate. As bearing out this idea, Brefeld-^ has observed 

 that the envelope is most strongly developed in those species on typical water- 

 plants, while it is less complete or only rudimentary on bog-plants. The 

 sppre-body can remain in water for a considerable time, and the spores ger- 

 minate at the surface or in moist air. 



The spores on germination produce an undivided germ-tube, which 

 gives rise to a whorl of long spindle-shaped conidia. They directly produce 

 smaller secondary conidia in various branching chains, and in a nutritive 

 solution they form an unlimited number of aerial sprouting yeast-like conidia 

 in direct succession. 



The conidia may also give rise to hyphae Avhich branch and again pro- 

 duce at various spots chains of conidia. 



There is here again a clear distinction between the parasitic form pro- 

 ducing spores which give rise to germ-tubes, each with its apical whorl of 

 conidia, and a saprophytic form in which the conidia thus produced sprouted 

 directly in a yeast like manner. 

 Australian species, 1. 



Lijtkrum. 

 68. Doassansia winteriana (Wint.) Magn. 



Mao-nus, Berlin, Verh. Bot. Ver. XXXIL, p. 253 (1890). 



Setchell, Exam. Doass. Ann. Bot. VI., p. 18 (1892). 



Sacc. Syll. VII., p. 505 (1888). 



Doassansia punctiformis Winter, Rev. Myc. VIII., p. 207 (1886). 



Sori on both surfaces of leaf, globose, punctiform, very minute, scattered 



or somewhat gregarious, brownish. 

 Spores numerous, collected into a ball, rounded to polygonal, isodiametric, 

 and 10-12 /lj diam. or a little elongated reaching 16 x 10*5 /t; epi- 

 spore thin, equal, smooth, sub-hyaline ; cortex composed of one 

 layer of polygonal cells, with thick, brownish, minutely granulated 

 walls. 



