366 BOTANICAL GAZETTE [may 
stand the pathological reactions of the diseased plant. Only in this way shall 
we be able to remove the causes or protect the plant against them or assist it 
to recover. 
If, then, we desire to find a safe remedy, we must know all that is 
possible to know concerning the disease. As a link in the chain 
of evidence this paper is presented, with the hope that it may 
serve to extend knowledge of the reaction of leaf tissue to fungous 
invasion. 
Historic 
The relations between parasitic fungi and their host plants are 
of various kinds. The subject might be divided into two parts: 
(1) the changes in the fungi when grown upon various substrata, 
and (2) the effects of the fungus upon its host plants. Among 
the latter we can easily distinguish two classes, though one class 
is dependent upon the other; those changes which are disturbances 
of the physiologic processes, and those which are changes in the 
morphologic structure. 
As we are to deal with the latter class in this paper, we shall 
turn our attention to the investigations on pathologic morphology 
which have previously been reported. The two phases which we 
must consider are (1) the anatomic and histologic, dealing with 
abnormal organs and tissues, and (2) the cytologic, dealing with 
abnormal cell structures. 
Various pathologic modifications of the floral organs have 
been noted. Motzrarp (48) described various changes in flowers 
caused by Peronospora, Cystopus, and other fungi, as well as by 
insects. WAKKER (84), in his most useful paper, reported addi- 
tionally a number of abnormalities in some or all the organs of 
various flowers. The reproductive organs and corolla of two species 
of Teucrium are attacked and changed in structure by the larvae of 
Copium (HOUARD 29, 32). Galls on the flowering parts of Euphor- 
bia Cyparissias also were described by Hovarp (30, 31). The 
changes which Warp (86) cited as occurring in the buds of Lilium 
candidum are less striking but none the less interesting. The 
effects of Cystopus candidus upon the various organs of its host as 
described by EBERHARDT (19, 20) are notable. 
