338 Transactions British Mycological Society. 



black, liberated by the decay of the host tissue. Spores spherical 

 to oval, measuring 17-20/x in diameter. Spore-membrane thick, 

 smooth, dark brown. Germination of spores not observed. The 

 spores and hyphae occur in the cortex and pith of the host 

 plant and are also frequently found in vascular tissue. Hyphae 

 forming pseudo-parenchymatous masses in the intercellular 

 spaces of host. Host plant Lamium album. Found at Chalfont, 

 Stroud, Gloucestershire, by Mr W. F. Drew. 



Morphology and Cytology o/M. Lamii and comparison 

 with other Genera. 



Such features in the morphology and cytology of the fungus 

 as the small amount of the material available permitted to be 

 ascertained will now be described. The hyphae of the fungus 

 run between the cells of the host plant and at the intercellular 

 spaces they often become massed, closely interwoven, and fre- 

 quently septate so that they form a pseudo-parenchymatous 

 body at these spots (fig. 2). 



Haustoria are developed at numerous points and these pene- 

 trate the cell wall and form much branched, coralloid structures 

 within the host cell (figs. 5 and 10). They usually attain a con- 

 siderable size and form a conspicuous feature in the morphology 

 of the fungus. They resemble a bunch of grapes in form, and 

 are seen to consist of a series of very short branchlets which 

 arise from the apex of a common carrying thread and each of 

 which is dichotomously forked at its end (fig. 6). The main 

 thread of the haustorium arises as an ordinary lateral branch 

 from one of the intercellular hyphae. No appressorium could 

 be seen such as Lutman (1910) described in Entyloma Nym- 

 phaeae (Cunn.) Setch. 



Lutman also found in his plant that the host cell nucleus fre- 

 quently becomes enclosed in a tangled knot formed of the haus- 

 torial branches. In Melanotaenium Lamii the terminal branch- 

 lets of the haustorium have several times been observed to be 

 closely applied to the nucleus of the host plant so that this 

 body becomes partly enveloped by them (fig. 5) but this is not 

 a constant feature, and just as many cases can be observed in 

 which the haustorium and cell nucleus remain widely sepa- 

 rated from one another (fig. 10) as those in which a closer re- 

 lationship is established between them. 



In spite of a number of works on the subject our knowledge 

 of the cytology of the Ustilagineae is still very incomplete. Not 

 only is the available information about any of the genera of this 

 family contradictory but many genera have never been investi- 

 gated at all. The genus Melanotaenium is among the latter and 

 the few facts ascertained and described below may form the 



