44 FUNGI. 
through all the genera to illustrate this chief feature of coloured, 
septate, rather rigid, and mostly erect threads, bearing at some 
point spores, which in most in- 
stances are elongated, coloured, 
and septate. 
Mucepines.—Here, on the other 
hand, the threads, if coloured at 
all, are still delicate, more flexuous, 
with much thinner walls, and never 
invested with an external cortical 
layer. One of the most important 
and highly developed genera is 
Peronospora, the members of which 
Fic. 26.—Acrothecium simplez. are parasitic upon and destructive 
of living vegetables. Itis to this genus that the mould of the 
too famous potato disease belongs. Professor De Bary has done 
more than any other mycologist in the investigation and eluci- 
dation of this genus ; and his mono- 
graph is a masterpiece in its way.* 
He was, however, preceded by Mr. 
Berkeley, and more especially by Dr. 
Montagne, by many years in eluci- 
dation of the structure of the flocci 
and conidia in a number of species.+ 
In this genus, there is a delicate 
mycelium, which penetrates the in- 
tercellular passages of living plants, 
giving rise to erect branched 
threads, which bear at the tips of 
their ultimate ramuli, sub-globose, 
ovate, or elliptic spores, or, as De 
Bary terms them—conidia. Deeply seated on the mycelium, 
within the substance of the foster plant, other reproductive 
bodies, called oogonia, originate. These are spherical, more or 
Fic. 27,.—Peronospora Arenarie. 
* De Bary, ‘‘ Champignons Parasites,” in ‘Ann. des Sci. Nat.” 4™ sér, vol. xx. 
t Berkeley, ‘‘On the Potato Murrain,” in ‘Journ. of Hort. Soc. of London,” 
vol. i. (1846), p. 9. : 
