Apr. 3-sept. 23, 1916 Illustrations xix 



n'-CROTONic Acid, a Son, Constituent 



Page 

 Plate CXIV. Fig. i. — o-Crotonic acid from soil. Fig. 2. — Synthetic a-cro- 



tonic acid 1046 



TEXT FIGURES 

 Climatic Conditioxs as Related to Cercospora beticola 



Fig. I. Cercospora beticola: A, Section of ovenvintered sugar-beet leaf show- 

 ing embedded sclerotia-like body, o, with a mass of old conidio- 

 phores, b, from which a new conidium, c, was produced. D, Produc- 

 tion of rather typical conidiophores, b, and conidia, c, from a sclero- 

 tia-like mass, a, taken from overwintered host material and placed 

 in hanging-drop cultures 22 



2. Curves of the maximum and minimum soil and air temperatures for 



the period from December 5, 1912, to March 13, 1913, at Rocky Ford, 

 Colo., and air temperatures from December 5, 1913, to March 13, 

 1914, at Madison, Wis., together with the periods that snow covered 

 the ground 28 



3. Curves of the maximum and minimum soil and air temperatures for 



Rocky Ford, Colo., from March 13 to June 17, 1913, and for Madison, 



Wis. , from March 13 to June 17, 1914 29 



4. Curves of the maximum and minimum temperatures and relative 



humidities and the number of hours that the humidity remained 

 above 60 from noon of the preceding to noon of the given day among 

 sugar-beet plants and in the air 5 feet above the field, together v/ith 

 the field rainfall and irrigation records. June 11 to August 2, 1913, 

 at Rocky Ford, Colo 32 



5. Ciu-ves of the maximum and minimum temperatiwes among sugar-beet 



plants and at the Weather Bureau station, and the seasonal rainfall 

 records at Madison, Wis., in 1914, and the number of hours that the 

 humidity remained above 60 among the sugar-beet plants in the 

 field at Madison, Wis., in 1914, and at Rocky Ford, Colo., in 1913 .... 34 



6. Ciu-ves of the leaf spot history series, showing the production of conidia 



on different dates from June 24 to September 19, 1913, at Rock}' 

 Ford, Colo 48 



7. Curves of the maximum and minimum temperattues and humidities, 



the number of hours that the humidity remained above 60 from 

 noon of the preceding to noon of the given day among the plants, 

 and rainfall and irrigation records, taken in a medium-early sugar- 

 beet field from June 10 to September 22, 1913, at Rocky Ford, Colo. . 51 



8. Curves of the comparative production of conidia on the upper and 



lower surfaces of the leaf spots, representing series E, K, N, and 



G of Table V and figure 6. Rocky Ford, Colo., 1913 52 



9. Curves of the 2 -day average increases in the number of leaf spots per 



plant in a. medium-early and an early sugar-beet field, from June 



18 to September 19, 1913, at Rocky Ford, Colo 54 



10. Curves of the maximum and minimum temperatiu-es and relative 

 humidities and the number of hours that the humidity remained 

 above 60 from noon of the preceding to noon of the given day among 

 the sugar-beet plants of a medium-early and an early field. August 

 2 to September 21, 1913, at Rocky Ford, Colo 58 



