42 
On the root. It has recently been found that the crowns and roots 
may also become involved, resulting in the long-known “brown rot’’ of the 
roots. If specimens are available study, NOTING :— ; 
21. The firm more or less dry brown decay of the tissue. The 
entire diameter of the root is involved. Compare with specimens of the 
so-called ‘‘black rot” of the roots. 
ETIOLOGY 
There are two pathogenes which cause Botryris blights of peonies. 
The small-sclerotial species is Botrytis paeoniae Oudemans. The large- 
sclerotial species is Botrytis (species?). The Botrytis paeoniae Oudemans 
appears to be the more common and destructive and is the one here con- 
sidered. ; 
Life-history. This fungus exhibits in its life-history both primary 
and secondary cycles with characteristic pathogenic and saprogenic 
hases. 
The Primary Cycles are initiated and completed, chiefly at least, 
on the young shoots which become diseased shortly after they come up 
in the spring. 
Pathogenesis. So far as is known conidia alone constitute the 
primary inoculum. These are produced in early spring from overwintered 
mycelium in the old diseased stubble or the stems on the ground. Pos- 
sibly also from germinating sclerotia in the old stems. 
Diseased stems have been brought in from the field and placed in moist- 
chambers. Examine the material and OBSERVE :— 
22. The numerous tufts of brown conidiophores covered with 
grey conidia,—the primary inoculum. 
SKETCH to show these conidial clusters on the stems. 
Mount some of the conidia and oBSERVE :— 
23. Their form, size and color. These conidia are carried by the 
wind and insects, chiefly ants, to the young shoots that are coming up 
nearby. Here they lodge and if conditions of moisture and temperature are 
favorable they germinate and penetrate the tender young tissues. Study 
the germinating conidia on the slides provided. pRaw. 
After penetration by the germtube, infection occurs, the first evidence 
of injury showing in two or three days. The mycelium ramifies the tender 
tissues in all directions killing them presumably by toxines which it se- 
cretes. 
Make thin sections of diseased stems provided and stupy:— 
24. The morphology of the mycelium and its relation to the host- 
cells. Is it inter- or intracellular? DRaw. 
From the mycelium, conidiophores are soon thrust forth to the exterior 
and conidia quickly and abundantly produced. Make mounts of conidio- 
phores from diseased stems. OBSERVE :— 
25. Their form, structure and the way in which conidia are borne. 
DRAW. 
Saprogenesis. After the shoot dies the mycelium begins to form 
sclerotia at the surface of the lesion, especially below the surface of the 
soil, where moisture conditions are more favorable. 
Examine the sclerotia growing in pure cultures or on diseased shoots. 
COMPARE :— 
