214 DESCRIPTION OF A NEW BRITISH MOULD. 



informs me that our Mould is the Botrytis umbellata* of De- 

 candolle. 



BOTRYTIS UMBELLATA. 



Ofi a flat and smooth leaf, the decumbent filaments of this 

 Mould form a cobweb-like mycelium, but on leaves with an 

 uneven surface, and on the stalks of herbs, the mycelium is 

 so filamentous and thin as to be scarcely perceptible ; while 

 the erect filaments are so numerous as to render the surface 

 downy or hirsute. The decumbent filaments are also slen- 

 derer than the others, but there is no difference in their 

 structure ; they are smooth hyaline membranous tubes jointed 

 at distant intervals, the joints alternately swollen and con- 

 stricted, but not regularly so, and when moistened with 

 water, the whole tube becomes swollen, tense, and cylindri- 

 cal. The erect filaments are two lines in height, of a grey 

 or cinereous colour, with a hoary sporuliferous head ; they are 

 sparingly and irregularly branched, and at the top four or 

 five short divergent branchlets form a sort of imperfect um- 

 bel, collecting, as it were, the sporules into a round heap or 

 summit. The main branches are either divergent or dicho- 

 tomous ; and many of the filaments are quite simple. The 

 sporules are ovate or elliptical, often marked with a septum, 

 sometimes transversely, and in others in a longitudinal direc- 

 tion ; and this septum disappears when the sporules are mois- 

 tened. The number of sporules is incalculable ; they fall from 

 the head and are found adherent to every fibre of the plant ; 

 and when this is shaken, they fly abroad in a little cloud. 



My friend Mr. Bowerbank examined this Mould with the 

 microscope. When highly magnified, many of the main fila- 

 ments exhibited slight protuberances, which were supposed 

 to be incipient branches ; these were sometimes opposed to 

 each other, and sometimes they were not quite in opposition. 

 The sporules varied considerably in size, and were ovate or 

 elliptical. Placed in water between glasses, after a lapse of 

 two days it was found that most of the sporules had germina- 

 ted, each emitting a single filament, which was sparingly and 

 irregularly branched, and contained some very minute gra- 

 nules. 



• Lam. et Decand. PI. Pran9. ii. 71. Duby Bot. Gall, ii. 921. 



