178 



FUNGI. 



threads of Tilletia* and similar acts of conjugation, as observed 

 in some species of Ustilago. Whether this interpretation should 

 be placed on those phenomena in the present condition of our 

 knowledge is perhaps an open question. 



Finally, the spermogonia must be regarded as in some occult 

 manner, which as yet has baffled detection, influencing the per- 

 fection of sporidia f In Rhy- 

 lisma, found on the leaves of 

 maple and willow, black pitchy 

 spots at first appear, which 

 contain within them a golden 

 pulp, in which very slender 

 corpuscles are mixed with an 

 abundant mucilage. These 

 corpuscles are the spermatia, 

 which in Rhytisma acerinum 

 are linear and short, in Rhy 

 tisma saUcinum globose. When 

 the spermatia are expelled, the 

 stroma thickens for the pro- 

 duction of asci and sporidia, 



Fio. 101. Tilletia caries with conjugating i i n, j j i j 



cells which are afterwards developed 



during the autumn and winter. 



Several of the species of Hysterium also possess spermogonia, 

 notably H. Fraxini, which may be distinguished from the asci- 

 gerous perithecia with which they are associated by their smaller 

 size and flask-like shape. From these the spermatia are expelled 

 long before the maturity of the spores. In Hypoderma virgul- 

 torum, H. commune, and H. scirpinum, the spermogonia are 

 small depressed black capsules, which contain an abundance of 

 minute spermatia. These were formerly regarded as distinct 

 gpecies, under the name of Leptostroma. In Stictis ocellata a 

 great number of the tubercles do not pass into the perfect state 



* Berkeley, in '{ Jpurn. Hort. Soc.' ? vol. \l p. 107; Tulasne, "Ann. d. Sc. 

 Nat." (4 me ser.), vol. ii. tab. 12. 



t Tulasne, "New Researches on the Reproductive Apparatus of Fungi;" 

 "Comptes Rendus," vol. xxxv. (1852), p. 841. 



