544 NEW JERSEY AGRICULTURAL COLLEGE 



State of 1L42 inchos. Tlii< is the heaviest ])re(:-ipitatioii for a single 

 month during tlie iiftoon years that the writer has heen connected 

 with the Experiment Station. While there were excessive rains in 

 1897, there were also periods of drought during the growing season. 

 Thus a dry spell was broken by the lieavy storms of July, and these, 

 in turn, were followed by a dry September, with less than half of 

 the average rainfall. The conditions for an outbreak of the potato 

 rot fungi were not as favorable in ISO 7 as in 1889, when September 

 had double its average rainfall. However, the reports of the crop 

 correspondents show that there was considerable loss in the potato 

 fields. It is probably true that a wet July is very favorable to the 

 development of the potato rot, and wlien this is followed by large 

 rainfalls in August and September the crop is quite certain to suffer. 



In this report a table of the monthly rainfall since 1888 is pub- 

 lished, together with the averages for e<ieh month and each year 

 during the fifteen years. 



The accompanying plate (Xo. XIY.) is from Professor Galloway's 

 Report of Section of Vegetable Pathology, United States Department 

 of Agriculture, for 1888, and the explanations below are from the 

 same source: 



Fig. 1. Section through a diseased leaf, showing the mycelium in the tissues and 

 two external spore-bearing hyphse projecting through a stoma. 



Fig. 2. Conidia and conidiophores more enlarged The epidermis and stoma are 

 shown in the surface view. (F. L. Schribner, del.) 



Fig. 3. A series of drawings, representing successive stages in the development of a 

 conidium : a, end of conidiophore slightly swollen ; b, c, successive stages in 

 growth of the conidium ; d, the conidiophore has pushed on, leaving the 

 conidium already formed, attached to an enlargement below the point, and 

 has begun to form another conidium on the end; e, the first-formed conidium 

 has fallen from the enlargement of the conidiophore at g, and the second 

 conidium formed is in turn left behind by the growing conidiophore, which is, 

 forming a third conidium at the end. 



Fig. 4. Mycelium in the tissue of a potato tuber. (F. L. S., del.) 



Fig. 5. Series of figures representing the germination of a conidium : «, mature coni- 

 dium ; b, same, after remaining some time in water, five vacuoles have made 

 their appearance ; c, the contents are segmented into five distinct parts, each 

 of which is provided with a vacuole ; d, the exospore has ruptured and the 

 zoospores are in the act of escaping ; e, free zoospore ; /, same a little later 

 the vacuoles have become smaller; g, same, still later, the cilia are gone and 

 the zoospore has come to rest; /(, beginning of germination ; i, k, I, successive 

 stages in the growth of the germ tube or first mycelium filament ; m, 

 entrance of germ tube into the leaf through a stoma. 



Fig. 6. Section of leaf, showing the penetration of a germ tube into the epidermis 

 through the cell wall. 



