l8o DIVISION II. COURSE OF DEVELOPMENT OF FUNGI. 



single spores (or perhaps several successively) are abjointed. The spores are narrowly 

 fusiform in shape, like the secondary sporidia of the promycelium, and it may be 

 assumed, though it has not been observed, that their mode of germination is the 

 same. They are formed on the mycelium before the resting-spores, and appear to 

 the naked eye as a slight sprinkling of flour or mould on the spot which is attacked 

 in the leaf. 



The most remarkable case of this kind was observed by Woronin in Tuburcinia 

 Trientalis. The resting-spores of this Fungus germinate in late autumn. The 

 mycelial primordia produced from the secondary sporidia penetrate into the young 

 subterranean shoots of Trientalis destined to pass the winter, and develope a mycelium 

 which also hibernates in their parenchyma. Next spring the mycelium spreads 

 through the whole of the shoot as it unfolds, and at first forms gonidia on the under 

 side of its leaves and afterwards the cluster of resting-spores, but more in the 

 stem than in the leaves. The gonidiophores are branches of the intercellular 

 mycelium and come out to the air through the stomata and lateral walls of the cells of 

 the epidermis, covering the whole of the surface of the leaf with a white down. 

 They are unbranched and subulate in form, and from the apex of each several 

 spores (gonidia) are successively abjointed one after another, which are pear-shaped 

 and not fusiform like the sporidia of the promycelium. Germ-tubes are put forth 

 by the gonidia on the moist surface of a leaf of Trientalis and penetrate into it, and 

 develope mycelia which are confined to small spots in the leaf, where they form clusters 

 of resting-spores but not gonidia. 



SECTION LVIII. According to the above well-ascertained facts the course of 

 development in the Ustilagineae (in species of Entyloma, in Ustilago Carbo, and Uro- 

 cystis occulta), where the process is the simplest, appears to be, that the resting- 

 spore produces a promycelium, and the promycelium the conjugating pairs, and the 

 mycelial primordia which proceed from them enter and develope in the host-plant 

 and produce fresh resting-spores. The first complication is caused by the production 

 of mycelial primordia, not directly from the conjugating pairs, but from secondary 

 sporidia proceeding from them, as happens almost invariably in some species of 

 Entyloma and in Tuburcinia Trientalis. Then comes in Entyloma Ranunculi, 

 E. serotinum, and in Tuburcinia Trientalis the interpolation of gonidia which are 

 formed on the endophytic mycelium and can produce similar mycelia. If we regard 

 the resting-spores as carpospores in the sense of section XXXIV, a point which will 

 be discussed further on, the secondary sporidia must be termed gonidia which have 

 been interpolated in the course of the development. Lastly, a mycelium can also 

 be produced on any dead substance which yields suitable nourishment and gonidia 

 on the mycelium, and it may at least be assumed that the gonidia are capable of 

 reproducing a mycelium forming carpospores. I have purposely avoided the general 

 use of the word gonidium in the preceding pages, though it will have to be used from 

 this time, in order to show by one example how the same object may and must have 

 different names when considered from different points of view and in different 

 connections. 



The facts that have been certainly ascertained are only these : that the species, 

 whose course of development has been really followed throughout, Ustilago Carbo, 

 U. destruens, Tilletia, Tuburcinia Trientalis, Entyloma and Urocystis occulta, all show 



