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328 8 1 Seractiral and 4 Physiol ical Botany els. 
ee Sy Ee. Ye tae ae | Si vine} t iiaanite iy i, ce “eat ws ig vee 
pith it. ‘The varlous uae: of development ‘of. the ergot 
rye received a number of: different names before their. con-" eet 
nection with one another had been ascertained. Thus — | 
the delicate mycelium from which ergot originally springs __ 
has been called Sphacelia segetum, the ergot itself Sclerotium — 
clavus, Secale cornutum |or ‘spurred rye’|, and the fructifica- 
tion which developes from it (Fig. 375), Cordiceps or Clavi- 
eps purpurea; the last be- 
ing the name now given to 
the Fungus. 
Mention must also be 
eases about which but little 
is yet known, and which 
have this in common, that 
they appear as black velvety 
coatings on the leaves, and 
made of a number of dis- 
especially on their upper 
Fic. 375.—Ergot : A, with four receptacles. side. There seems to be fre- 
brea size); B, longitudinal section : eg 
through a receptacle with its perithecia. quently, but not invariably, 
(Magnified.) a connection of alternation 
between the ‘honey-dew’! caused by aphides and these 
diseases, the aphides encouraging the settlement of the 
Fungi, Zorula and Cladosportum, which give rise to the 
tatter. 
A similar appearance is presented by vines attacked by 
the vine-mildew, Oidium Tuckert. ‘The course of this dis-— 3 
ease is, In its essential points, as follows :—A delicate white 
shining growth is seen, as a rule after the blooming-time, 
and at first on the under side of the leaves, then on all the 
young parts of the vine (Fig. 376), which finally invests 
these parts more and more completely, without, however, 
penetrating into the interior, as it only puts out short 
organs of attachment here and there. These drain the 
? Honey-dew is a sweet juice exuded by various species af Aphis; 
for believed by some to be an exudation from the leaf itself, A 
