116 
forth from their entire under surfaces, conidiophores bearing conidia. 
Such invaded plants are said to be suffering from ‘“‘systemic infection”’. 
(See text.) 
Systemic infection is very common in the case of Peronospora Ficariae 
in the buttercup, Ranunculus acris. Examine one of the diseased leaves 
of R. acris. NOTE:— 
15. That the conidiophores cover the entire under surface of 
the leaves. Where this occurs, one may be quite sure it is a case of ‘‘sys- 
temic infection’’ and not a local lesion. 
If fresh material is available, make sections through some part of 
systemically infected plants (crown or rootstock). Stain with methyl blue, 
wash thoroughly, cover and locate the mycelium in the tissues; inter- or 
intracellular? Haustoria? DRaw. 
The mycelium continues to live in the gradually weakening host, pro- 
ducing one crop of conidia each season from which primary infections, 
ieee or systemic, in character may arise. It eventually perishes with 
e host. 
REPORT 
1. If a gardener discovered some of his perennials to be suffering 
from systemic infection, what methods of control should he employ? 
ae If all the infections are local, what should be the treatment? 
y! 
2. Show in a graphic diagram the life-cycles of either of the 
pathogenes studied in this exercise. 
