XII 
Journal of Agricultural Research 
Vol. XIV 
Plate 77. Plasmodiophora brassicae: A.—Several xylem strands being forced 
apart by medullary infection. B.—A bundle that is beginning to be fan¬ 
shaped in cross section. 372 
Plate 78. Plasmodiophora brassicae: A.—A fibrovascular bundle that is almost 
semicircular in cross section. B.—A strand that is almost circular in 
cross section. 372 
Plate 79. Plasmodiophora brassicae: Distribution of the parasite in the 
tissues of two different clubs at the time of spore formation. A.—30.9 per 
cent of the surface of the photograph is occupied by spore masses. B.— 
28.8 per cent of the photograph is occupied by these masses.. 372 
Plate 80. Plasmodiophora brassicae: Tissues from two other clubs—A.—28.8 
per cent of the photograph is occupied by the spore masses. B.—An 
unusual distribution of the parasite. 372 
Life History of Pemphigus populi-transversus 
Plate 81. Pemphigus populi-transversus: A.—Young fundatrix, first instar. 
B, a. b, c.—Beginning of galls on cottonwood leaves. C.—Adult fundatrix 
with cottony secretion removed, D.—Winged sexupara from roots of 
Brussels sprouts. E-—Wingless virgogene from roots of Brussels sprouts. 
F.—Male. G.—Oviparous female. H.—Antenna of fundatrix. I.—An¬ 
tenna of wingless viviparous female from Brussels sprouts. J.—Antenna 
of winged fundatrigenia from gall. K.—Antenna of winged sexupara 
from Brussels sprouts... 594 
Plate 82. Pemphigus populi-transversus: A.—Gall on poplar cutting. B.— 
Gall shown in A, enlarged to nearly natural size.. 594 
Plate 83. Pemphigus populi-transversus: Variation, in size of galls and 
location.on leaf petioles of Populus deltoides t Baton Rouge, Ea., September 
r 9 T 6. 594 
Plate 84. A.—Gall of Pemphigus populi-transversus , lips not protruding. 
B.—Gall of Pemphigus populi-transversus , lip protruding. C.—Gall of 
Pemphigus populi-ramulorum. D.—Beginning of gall of Pemphigus 
populicaulis. E.—Full-grown gall of Pemphigus populicaulis . F.—Turnip 
seedlings, showing injury by Pemphigus populi-transversus: a , infested; 
b y control.... 594 
Plate 85. Pemphigus populi-transversus: F.—White cottony secretion at 
roots of Brussels sprouts due to presence of Pemphigus populi-transversus .. 594 
TEXT FIGURES 
True Nature of Spinach-Blight and Relation of Insects to Its Trans¬ 
mission 
Fig. 1. Graph representing the average lengths of the various stages in the pro¬ 
gress of spinach-blight. 5 
Correlation between the Percentage of Fat in Cow's Milk and the 
Yield 
Fig. 1. Graphs showing the averages of the milk yield for the different ages of 
cows. 70 
2. Graphs showing the averages of percentages of butter fat for different 
breeds of cows. 70 
