172 



DIVISION II. COURSE OF DEVELOPMENT OF FUNGI. 



but pairs thus united are to be seen in a few hours after ejection ; the two halves 

 of each pair are in open communication, and in most cases also swollen to a 

 larger than their original size. Each of these double spores is capable of germinating 

 under conditions which will be described in section XCVI ; one of the halves 

 puts forth a tube which takes the whole of the protoplasm of the pair, and pene- 

 trating into a suitable host developes there at once into a new mycelium, which 

 forms resting-spores. No further stage of the development is known. 



The plant in question with its peculiar and simple course of development is at 

 present an isolated form ; only the resting-spores are at present known of a second 

 species, Protomyces pachydermus, Thiimen 1 , which grows on the Cichoraceae and has 

 probably a similar history. 



SECTION LIV. The Ustilagineae are endophytic parasites in phanerogamous 

 plants. Their mycelium, which usually spreads through the intercellular spaces 

 of the host, consists of slender hyphae with comparatively long segments. In 

 some species it has haustorial branches each with a tuft of sinuous branchlets 



FIG. 79. Protomyces macrosporus, Unger. a a mature resting-spore in the dormant state with the remains of the hypha which 

 bears it. * further development of the same when grown in water ; the protoplasmic body surrounded by the innermost membranous 

 layer (the inner cell) is swelling and escaping from the ruptured outer membranous layer, cc development of spores in the escaped 

 inner cell, the sporangium, c the parietal protoplasm, d the same divided into spores. In e the spores are rounded off and separated 

 from the remainder of the parietal protoplasmic layer. Magn. 390 times. 



which penetrate into the cells of the host (see page 20). Resting-spores or 

 more shortly spores, are formed in or on the host, either, as in Entyloma, in all 

 parts of the mycelial hyphae, or in special branches different from those first 

 formed. These sporogenous branches of the Fungus form very numerous ramifica- 

 tions, and are usually woven together in great numbers into compact masses of definite 

 shape and occupying definite spots ; they are generally found inside the plants attacked 

 by the Fungus, especially in the flowers and fruit or in parts of them that are 

 diseased and swollen, and there they in great measure destroy and consume the 

 tissue; less often (for instance Sorosporium Saponariae, Ustilago Tragopogonis, 

 U. hypodytes) on the surface of the part attacked which they closely cover up. 

 We may therefore in these cases speak of spore-producing bodies, compound 

 sporophores, in the sense of section XII. The Entylomeae, on the other hand, are 

 simple hyphomycetous forms, and other species, those especially which live in 

 leaves (species of Tilletia and Urocystis), are intermediate between the two extremes. 



1 Hedwigia, 1874 and 1878, p. 124. 



