CHAPTER V.— COMPARATIVE REVIEW. — USTILAGINEAE. 



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abjunction ; all the sporogenous hyphae divide, according to Winter, by transverse walls 

 arising from the extremities of their curved terminal branches in basipetal succession 

 into short members, which develope into spores united together in pairs. 



The development of the spores of Ustilago may be briefly described in about 

 the same words, only in this case the ripe spore-cells are not united in couples, 

 but are isolated and free. The terminal ramifications of the sporogenous hyphae 

 are in some species (U. Ischaemi according to Winter, U. hypodytes according to 

 my old account) slender and filiform, but they are usually furnished with many 

 tufts of short branches, so that they have a peculiar clustered and lobed appearance 

 (Fig. 82). Ustilago has the further peculiarity that the membranes of the hyphae 

 swell strongly into a jelly synchronously with or even before the basipetal segmentation 

 by cross walls into short isodiametric members, which also takes place in them. The 

 protoplasm of each individual member is therefore soon surrounded by a broad hyaline 



FIG. 81. a and b Entyloma Calendulae. a mycelial 

 filament with two young resting-spores. * resting-spore 

 germinating; the front pair of primary sporidia in the 

 whorl shows conjugation at the base, c and d Entyloma 

 Ungerianum, DeBary. cagerminating resting-spore; four 

 primary sporidia conjugating by pairs at their apices, d the 

 same specimen seven hours later ; commencement of the 

 abjointing of a secondary sporidium (gonidium) on each 

 pair. Magn. 600 times. 



FlG. 82. Development of the spores oi Ustilago 

 Tragopogonis ; successive stages of the development 

 according to the letters, a sporogenous branch, just 

 appearing on the surface of the young corolla of Trago- 

 pogon pratenszs and beginning to form a tuft of branch- 

 lets, d spore-tuft with several ripe spores, the episporium 

 of which is coloured a dark violet and furnished with 

 reticulate thickenings. Magn. 300 times. 



gelatinous sheath (Fig. 82 b, c), and forms inside it a relatively small almost homo- 

 geneous and strongly refringent nucleus-like body. The definitive membrane of 

 the spore is then formed on its outer surface inside the gelatinous envelope, and 

 developes with the protoplasm into the comparatively large spore. As growth 

 proceeds the gelatinous sheath becomes more delicate and paler and disappears 

 altogether when the spore has reached maturity {b-d). 



In the genera Urocystis, Sorosporium, and Tuburcinia the ripe spores are 

 joined together from two up to a considerable number in a cluster and are each 

 provided with a persistent or temporary special envelope. The development of the 

 cluster is not clearly known in all points. In Urocystis, according to Wolff and Winter, 

 the first beginning of a cluster is represented by a turgid and often curved branch from 



