216 BOTANICAL GAZETTE. [| September, 
colors and manner of flight, also imitates them in resting 
lightly on the flowers and extracts pollinia less frequently 
than any wasp I have seen. 
EXPLANATION OF Puate XII.—Fig. 1, Gynostegium of Asclepias verticil- 
data L., with one hood removed. Fig. 2, Same, uf Aselepias purpurascens L. 
ig. 3, Gynostegium of Acerates longifolia Ell. Fig. 4, Sketch of Bombus 
scutellaris Cress., with pollinidof Acerates longifolia. ig. 5, Sketch of face 
f Cerceris bicornuta Guér., with pollinia of Acerates longifolia. Fig. 6, Pol- 
linia of Acerates viridiflora Ell.; one in stigmatic chamber with tubes emitted. 
Fig. 7, Corpusculum of same, “spiked” and displaced by caudicle of inserted 
pollinium. 
The “Curl” of Peach Leaves: a study of the abnormal structure 
induced by Exoaseus deformans.' 
ETTA L,. KNOWLES. 
(WITH PLATE XIII.) 
The fungus which causes the disease of peach leaves, 
known as ‘the curl,” a pears very soon after the leaf un- 
folds. The following observations were made from alcoholic 
material gathered May 30, and June 8, 1887. The fungus 
the time of concluding this work, at the end of June, but was 
less abundant at that time than early in the month. 
A study of the structure of the normal leaf was first made 
to serve as a basis of comparison with that of the diseased 
leaf. The drawings were all made with the camera. Fig: 
represents a cross section of a healthy peach leaf, a being the 
upper and 4 the lower surface. The epidermis consists of a 
sh a very thin, delicate cuticle. The epidermal cells of the 
Sn surfaces differ considerably in shape and size, as show? 
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ontributions from the Botanical Laboratory of the University of Michigan, il 
