1897, The Bacterial Diseases of Plants: 123 
occasion nearly an entire box of the best plates in my endeavor 
to secure a picture of a pair of nestling Pewees (Contopus virens) 
in their nest. In the pictures the birds looked as though they 
had been snowed on. Cutting off the light from above in a later 
attempt rectified this defect. One good way to study the effect 
of the light, is upon the ground glass of the camera, when the 
subject has been carefully focused upon it—and I think it will 
be found a safe rule in many cases to make the exposure when 
a light cloud partially veils the sun’s face. All such matters, 
however, can only be gained by experience ; and to pass through 
this, the best of all schooling, one must be pre-armed with an 
enormous stock of the best kind of patience, with a slight 
reserve fund of the same article on hand in the event of a run 
upon the original supply. 
The picture of the Cedar Birds taken in this way is repro- 
duced in Plate I, January number of the NATURALIST. 
THE BACTERIAL DISEASES OF PLANTS: 
A CRITICAL REVIEW OF THE PRESENT STATE OF 
OUR KNOWLEDGE. | 
By Davik F. Smit. 
(Continued from p. 41.) 
VI. 
Ill. THE POTATO (SOLANUM TUBEROSUM L.) 
1. THE GAS-FORMING WET-ROT OF THE TUBERS (1891). 
(1) THE DISEASE: 
(1) Author, Title of Paper, Place of Publication, ete.—This dis- 
ease was studied by Dr. Ernst Kramer in 1890-91. His paper, 
entitled (40) Bakteriologische Untersuchungen über die Nassfäule 
