POLYMORPHISM. 187 
stance occurs with Puccinita violarum, Link., and Trichobasis vio- 
larum, B.; with Puccinia fallens, C., and Trichobasis fallens, Desm.; 
also with Puccinia menthe, P., and Trichobasis Labiatarum, D.C. 
In Melampsora, again, the prismatic pseudospores of Delampsora 
salicina, Lev., are the winter fruits of Lecythea caprearum, Lev., 
as those of Mfelampsora populina, Lev., are of Lecythea populina, 
Lev. In the species of Lecythea themselves will be found, as De 
Bary * has shown, hyaline cysts of a larger size, which surround 
the pseudospores in the pustules in which they are developed. 
A good illustration of dimorphism in one of the commonest of 
moulds is given by De Bary in a paper from which we have 
already quoted.| He writes thus:—In every household there is 
a frequent unbidden guest, which appears particularly on pre- 
served fruits, viz., the mould which is called Aspergillus glaucus.. 
It shows itself to the naked eye as a woolly floccy crust over 
the substance, first purely white, then gradually covered with 
little fine glaucous, or dark green dusty heads. More minute 
microscopical examination shows that the fungus consists of 
richly ramified fine filaments, which are partly disseminated in 
the substratum, and partly raised obliquely over it. They have 
a cylindrical form with rounded ends, and are divided into long 
outstretched members, each of which possesses the property 
which legitimatizes it as a vesicle in the ordinary sense of the 
word; it contains, enclosed within a delicate structureless wall, 
those bodies which bear the appearance of a finely granulated 
mucous substance, which is designated by the name of proto- 
plasm, and which either equally fills the cells, or the older the 
cell the more it is filled with watery cavities called vacuoles. 
All parts are at first colourless. The increase in the length 
of the filaments takes place through the preponderating growth 
near their points; these continually push forward, and, at a 
short distance from them, successive new partitions rise up, 
but at a greater distance, the growth in the length ceases, 
This kind of growth is called point growth. The twigs and 
* De Bary, ‘‘ Uber die Brandpilze” (Berlin, 1853), pl. iv. figs. 8, 4, 5. 
+ A. de Bary, on Mildew and Fermentation, in ‘‘ Quarterly German Magazine,” 
vol. ii, 1872. 
