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ILLUSTRATIONS 



PLATES 



Relation ok Carbon Bisulphid to Soil Organisms and Plant 



Growth 



Plate I. Plate cultures of soil organisms growing on agar: Fig. i. — Colonies of 

 organisms from untreated soil. Fig. 2. — Colonies from soil treated with 2 

 per cent of carbon bisulphid. Fig. 3. — Colonies from soil treated with 2 per 

 cent of carbon bisulphid and evaporated. Fig. 4. — Colonies from soil 

 treated with 2 per cent of carbon bisulphid, evaporated, and reinoculated 

 with 5 per cent of soil from an untreated jar 20 



Plate II. Fig. i. — Effect of varying amounts of carbon bisulphid on mustard; 

 A, B, soil untreated; C, D, soil treated with 0.5 per cent of carbon bisul- 

 phid; E, F, soil treated with i per cent of carbon bisulphid; G, H, soil 

 treated with 2 per cent of carbon bisulphid. Fig. 2. — Effect of carbon 

 bisulphid on clover in peat soil; .4. B, soil untreated; C, D, soil treated 

 with 2 per cent of carbon bisulphid. Fig. 3. — Effect of carbon bisulphid 

 on buckwheat in sand cultures; A, B, soil untreated; C, D, soil treated 

 with 2 per cent of carbon bisulphid 20 



Climatic Conditions as Related to Cercospora beticoLa 



Plate III. Cercospora beticola: Overwintering tests on the experimental field 

 at Rocky Ford, Colo., during 1912-13: Sugar-beet leaves infected with Cer- 

 cospora beticola (/) stored in soil in boxes, (2) buried in the groimd at dif- 

 ferent depths from i to 8 inches, and (j) left exposed above the ground in a 

 pile of hayed sugar-beet tops 60 



Plate IV. Field stations for the collection of weather data at Rocky Ford, 

 Colo., in 1913: Fig. i. — Weather shelter, anemometer, and rain gauge at 

 edge of sugar-beet field . Fig. 2 . — Weather shelter among beet plants, show- 

 ing hygrothermograph and cog psychrometer. Fig. 3. — Weather shelter of 

 the local Weather Bureau station about 3 miles from sugar-beet field 60 



OviPOsiTioN OF Megastigmus spermotrophus in the Seed of Douglas 



Fir 



Plate V. Oviposition of Megastigmus spermotrophus in the cones of Douglas fir: 

 Fig. I. — Type of cage in which the oviposition of Megastigmus spermotro- 

 phus was observed. Fig. 2, 3. — Female resting on cone with ovipositor 

 inserted 68 



Plate VI. Oviposition of Megastigmus spermotrophus in the cones of Douglas 

 fir: Figs, i, 2. — Two positions of female on surface of cone with ovipositor 

 inserted. Fig. 3. — Female resting on cone with ovipositor inserted 68 



Plate VII. Oviposition of Megastigmus spermotrophus in the cones of Douglas 

 fir: Fig. i. — Female in act of withdrawing ovipositor from cone. Fig. 2. — 

 Section through a Douglas fir cone on which a female has been killed while 

 in the act of ovipositing. Fig. 3. — A portion of same cone and dead female 



with ovipositor inserted 68 



vn 



