CHAPTER V. — COMPARATIVE REVIEW. — USTILAGINEAE. 



177 



episporium is almost or altogether colourless. The envelope-cells which adhere 

 to the spores in Urocystis have likewise pale-coloured membranes at the time of 

 maturity, and their contents are almost entirely watery. 



The germination of the resting-spores takes place when they are sufficiently 

 supplied with moisture and have absorbed it to a sufficient degree. The form 

 differs according as only water is supplied to the spores or nutrient matter also 

 dissolved in the water. 



In the first case a short germ-tube is emitted, which takes the protoplasm of 

 the spore and developes into a promycelium in the sense of section XXXI (p. 111). 

 In most species the promycelium remains in connection with the membrane of the 

 spore, in a few, as Ustilago Vaillantii, it soon separates from it. To this rule of 

 development there are a few individual and specific exceptions which will be con- 

 sidered presently. The further development is as follows : — 



1. Shoots are put forth acrogenously or laterally at the cost of the protoplasm 

 and are abjointed; these in the terminology 

 which has been proposed would be sporidia 

 (of the first order). The particular forms 

 which their development assumes vary much 

 in the several species; the chief ones, with 

 which isolated intermediate or divergent kinds 

 can easily be connected, are these : — 



a. A whorl or circle of narrowly cylin- 

 drical or subulate sporidia (' Kranzkorper ') 

 shoots out from the obtuse and compara- 

 tively broad apex of the promycelium. They 

 appear simultaneously; their number in a 

 whorl is different in different species and in- 

 dividuals, varying between 4 and 10. This 

 mode is characteristic of most species of En- 

 tyloma (Fig. 81), and for Tilletia (Fig. 83), 

 Tuburcinia, and Urocystis. 



b. The promycelial tube is divided by 

 transverse walls into a series of two or more 

 short cells, and from these are abjointed, 

 usually at their acroscopic extremity, a number 



of elongated or rod-like shoots as sporidia. This is the process in Tolyposporium 

 Junci, Woronin, and in many species of Ustilago, for instance in U. Tragopogonis 

 (Fig. 84 B), U. flosculorum, U. utriculosa, U. Cardui, U. Kiihniana, and some others. 



c. The spore emits a simple, or in a very few cases a branched, short, slender 

 promycelial tube, and from this is abjointed one cylindrico-fusiform sporidium 

 or several in a row one after another (Ustilago longissima, Fig. 84 A, Thecaphora 

 Lathyri according to Brefeld). 



2. The slender promycelial tube, which sometimes puts out one or two branch- it- 

 like protuberances, is divided by transverse walls into a few cells from which single 

 sporidia are abjointed or sometimes none. This is the case with Ustilago Carbo 

 (Fig. 84 C), U. destruens, and, according to Woronin, with Thecaphora hyalina. 



[4] 



FIG. 83. Tilletia Caries, Tul., germinating. In a pri- 

 mary sporidia beginning to shoot out from the promyce- 

 lium/. In b the primary sporidia s of the promycelium 

 P conjugated in pairs. In c a germ-tube x proceeding 

 from a pair of primary sporidia s ; s' a secondary spori- 

 dium or gonidium. After Tulasne. Magn. 460 times. 



