220 PHYLUM VII. CARPOMYCETEAE 
ally penetrate downward some centimeters into the unin- 
jured bark, and remain dormant there until the following 
spring, when they begin the growth which results in the 
production of a new knot, as described above. 
359. To this order belongs the Ergot (Claviceps), a 
common parasite upon heads of rye, and also many of 
the black growths upon the bark and wood of trees. 
Many species produce black spots upon living leaves, 
while many others occur upon dead leaves and twigs. 
360. The Closed Fungi include a large number of 
exceedingly injurious species; they often attack and 
destroy not only plants, but also insects, upon which 
their ravages are sometimes very great. 
Tue Mitprws (ORDER PERISPORIALES) 
361. These plants, which are mainly parasitic, are 
composed of branching septate filaments (hyphae) which 
form a white or dark web-like film upon the surface of the 
leaves and stems of their hosts. There are both sexual 
and asexual spores, and of the latter there are in some 
cases two or three different kinds, which are produced 
earlier than those that result from a fertilization. 
362. In the Powdery Mildews (Family Erysiphaceae), 
which are all parasitic, the jointed filaments closely 
cover the leaves and other tender parts 
of many plants, and draw nourishment 
from them by means of suckers (hausto- 
ria), which project as irregular out- 
growths from the side next to the epi- 
FTG eee *® dermis. These suckers apply them- 
selves closely to the epidermal cells, and 
penetrate them. 
363. The crossing and branching filaments soon send 
up many vertical branches, which continue to form new 
