26 
POPULAR SCIENCE REVIEW. 
gillus or Penicillium originated from the spores of the Muce- 
dine which were sown, but perhaps never germinated. When 
two moulds proceed apparently from the selfsame mycelium, 
judgment may be pronounced too hastily, for the mycelium of 
both may be distinct, though interlaced together ; the safest 
conclusion being based on two forms of fruit when developed 
upon the same thread. Beyond this, there is always room for 
doubt. Hence it will be seen how difficult it is to prove 
dimorphism in moulds under such conditions. In many case& 
it is more presumption than proof. These remarks are not 
made with the view of discrediting the conclusions of such 
observers as Professor De Bary and the brothers Tulasne, but 
rather as a caution against assuming as fact that which is only 
conjecture. 
Messrs. Tulasne, in their splendid work, “ Selecta Fungorum 
Carpologia,” have given a great number of instances of polymor- 
phism. We have no reason to doubt that in many cases, perhaps 
most, they are quite correct, but even some of their conclusions 
require verification before they can be accepted as established 
fact. As an illustration of the results determined with regard 
to one species by these authors, we may instance the very 
common Sphceria (Plceospora') herbarum. It occurs on the 
dead stems of herbaceous plants, on the leaves of some trees, 
and even sometimes on decaying Algae . On pea and bean 
stems it is usually plentiful. In fact, it is almost the commonest 
Sphceria , and easily recognised. The sporidia are, of course, 
contained in elongated, transparent, membranaceous asci ; they 
are of a yellowish-brown or amber colour, ovate-oblong, and 
divided by numerous septa, with transverse divisions. The 
asci are enclosed within carbonaceous perithecia. 
Equally as common, and even more so, is a mould which 
forms sooty or dark olive spots, or patches, on all kinds of 
decaying vegetable substances. This is called Cladosporium 
herbarum . It may be characterised as cosmopolitan, and one 
of the commonest, if not the commonest, of fungi. Under the 
microscope this mould consists of a profuse mycelium, from 
which arise tufts of jointed threads, mixed with elliptical or 
elongated spores, ultimately septate. This mould is one con- 
dition, according to M. Tulasne, of Sphceria herbarum . 
Another condition of the same plant is a very pretty mould 
found mixed with, or parasitic upon, the Cladosporium , and 
known as Alternaria tenuis . This species is figured in Corda’s 
“ Prachtflora,” and consists of chains of spores resembling in- 
verted jointed clubs. The joints are also transversely divided,, 
as in the Sphceria sporidia. 
A third form of the same species is that named by Rev.. 
M. J. Berkeley Macrosporium sarcinula , which is developed 
