CHAPTER V. COMPARATIVE REVIEW, USTILAGINEAE. 173 



It is true that most of these compound sporophores have no independent 

 form of their own, for they merely fill cavities in the substance of the host, though 

 these cavities owe their existence and particular shape to the Fungus ; or they 

 are flat layers something like a Thelephora covering superficial portions of the 

 plant. Yet the' growth of many of these bodies evidently follows a single common 

 plan ; it is continued for a time at fixed spots by the constant formation of fresh 

 sporogenous branches which form a weft in the superficial layers, for example, on 

 the whole of their basal surface, and on removal from these spots comes to an end 

 or passes on to formation and maturation of spores. 



Most of these bodies consist only of sporogenous hyphae which are gradually 

 used up to form spores, so that heaps of spores only remain at maturity. But there 

 are species whose compound sporophores form other organs as well, which accom- 

 pany or envelope the spores. Rudimentary forms of this kind are perhaps to be 

 seen in the pellucid vesicles which Meyen discovered between the spores of Ustilago 

 longissima and which require to be further investigated, also in part at least in 

 the filaments in the spore-masses of U. olivacea which are still unexplained. Cornu's 

 Doassansia, one of the Ustilagineae which is parasitic on water-plants and approaches 

 Entyloma in the structure and germination of its spores, forms its spores inside 

 a round closed receptacle, the wall of which consists of compact palisade-cells 

 belonging to the Fungus. Ustilago Hydropiperis has a much and distinctly differ- 

 entiated spore-receptacle, and might on that account be made a separate genus 

 under the name of Sphacelotheca. But the greatest amount of differentiation in 

 the compound sporophore is to be seen, according to Ed. Fischer's researches, in the 

 genus Graphiola, if it should prove really to belong to the Ustilagineae. 



We have said enough to show that the compound sporophores of the Ustilagineae 

 deserve more attention than has been bestowed upon them since Tulasne's first memoir. 

 Cornu's examination of Doassansia is only known to me from a preliminary and private 

 communication from the author, but a more detailed account of it is to be expected 

 shortly. The reader is referred to Ed. Fischer's own paper for his investigation of 

 Graphiola ; and we may proceed to give a description of Sphacelotheca, the parasite of 

 the flowers of Polygonum Hydropiper mentioned above, as an example of a highly 

 differentiated compound sporophore, though the investigations of the year 1854, from 

 which we must draw our material, are old and in some points defective (Fig. 80). 



Sphacelotheca forms its compound sporophore in the ovule of its host. When 

 the ovule is normally and fully developed in the young flower, the parasite, which 

 always grows through the flower-stalk into the place of insertion of the ovary, sends its 

 hyphae from the funiculus into the ovule, where they rise higher and higher and 

 surround and penetrate its tissue to such an extent as almost entirely to supplant 

 it, and thus an ovoid Fungus-body of densely interwoven hyphae takes the place of the 

 ovule. The micropylar end of the integuments alone escapes the change, and remains 

 as a conical tip (Fig. 80 C, o) on the apex of the Fungus-body and gradually turns brown 

 and dries up. The Fungus-body is at first colourless and uniformly composed of much- 

 branched hyphae, which are woven together into a compact mass and have the gelatinous 

 walls of the simple sporophore of Ustilago to be described below. If it has retained its 

 ovoid form as it steadily increased in volume, differentiation begins first in the apical region 

 into a comparatively thick outer wall which is closed all round, an axile columnar 

 cylindrical or club-shaped body, the columella, both parts remaining colourless, and a 

 dense spore-mass which fills the space between the two and becomes of a dark violet 

 colour (Fig. 80 C, D). The lower part which corresponds to the funiculus and chalaza 



