65 British Ui^edinecs and Ustilao^inece. 



Subjoined is a summary of his observations. The 

 mycelium pervades all parts of the affected plant, excepting 

 the roots. It consists of intercellular, branched, sparsely 

 septated, hyaline hyphae, having a diameter of from 2 to 

 3^t. It is most abundantly distributed in the cortical 

 tissues, and sends botryform haustoria (Plate VI, Fig. i) 

 into the adjacent cells. At certain places it gives off 

 smaller, more richly septate branches, unprovided with 

 haustoria, which are destined to form the spore-beds. This 

 is accomplished in the following manner : — A number of 

 straight and rather larger branches are given off, which 

 soon become curved and interwoven in various ways, gene- 

 rally more or less spirally, so as to form an entangled knot. 

 The spore-bed which this entanglement forms develops 

 spores from within outwards ; each spore-ball contains from 

 fifty to a hundred spores. The spores measure from 55 

 to 75^ in diameter, and consist of an endospore, containing 

 granular protoplasm, and an exospore. No gelatinization 

 of the spore-forming hyphae, such as takes place in the 

 spore-formation of Sorosporiiim sapoiiaricB, was observed. 



Tilletia. — The spore-formation in this genus was first 

 indicated by Tulasne,* afterwards by Kuhn,t who gave 

 a figure of the process ; but it is to Von Waldheim % 

 that we are indebted for the most detailed account. He 

 thus describes the process : The vegetative mycelium of 

 Tilletia tritici is nearly 2n in diameter. The swelling 

 and gelatinization of the spore-forming hyphae Is not so 

 marked as in Ustilago, so that the lumen of the hyphae 

 is never so contracted. Spore-formation begins by the 

 hyphae giving off pyriform buds, r5/i across (Plate VI_ 

 Fig. 4), in succession, from their sides ; these outgrowths in- 



* Tulasne, " i"^ Memoire sur les Ustilaginees comparees aux Urediiiees," 

 p. 27, ct seq. 



t Kiihn, " Krank. der Kulturgewachse," p. 56, t. iv. fig. 5. 

 X F. von Waldheim, loc. cit. 



