CHAPTER V.—COMPARATIVE REVIEW.—USTILAGINEAE. 175 
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 


Fic. 81. a and 5 Entyloma Calendulae. a mycelial FIG. 82, Development of the spores 0. Ustilayo 
filament with two young resting-spores. 64 resting-spore Tragopogonis; successive stages of the development 
germinating; the front pair of primary sporidia in the according to the letters. @ sporogenous branch, just 
whorl shows conjugation at the base. c and d Extyloma appearing on the surface of the young corolla of Trago- 
Ungertanum, De Bary. cagerminating resting-spore; four pogon pratensts and beginning to form a tuft of branch- 
primary sporidia conjugating by pairs at their apices. the lets. @ spore-tuft with several ripe spores, the episporium 
same specimen seven hours later; commencement of the of which is coloured a dark violet and furnished with 
bjointing of a dary sporidii idi on each reticulate thickenings. Magn. 300 times. 

pair. Magn. 600 times. 
gelatinous sheath (Fig. 82 2, 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 (d-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 
