EXPERIMENT STATION BULLETINS. 



659 



bottom 7 cm.) were arranged to serve the same office as the aluminum 

 shells used in the plant physiological laboratory. The lower third was 

 cut off and the top portion fastened to Petri dishes with paraffin. After 

 the paraffin had hardened, more melted paraffin was poured into the 

 dish and the pot containing the plant was set into this paraffin before 

 it hardened. Holes were made in the covers for the stem and corks. 

 (Plate 3, Fig. 2). The transpiration performance of the plants was 

 observed for a period of five days. May 2nd to 6th, inclusive, loss of 

 weight being made up daily. At the end of this time, the number of 

 leaves ranged from four to seven with leaflets on each leaf varying from 

 three to seven. 



Inoculations were made by placing two loopfuls of a pure culture sus- 

 pension upon the lower surface of each alternate leaflet of eleven plants. 

 The other plants were held as checks. The checks and inoculated plants 

 were kept in a moist chamber for a period of four days to insure strong 

 infection.^^ This was the only interval in which no weighings were tak- 

 en, otherwise every twenty-four hours from May 2nd to May 20th, weigh- 

 ings were made and water added to bring back the original weight ex- 

 cept that on May 12th, ten extra c. c. were added to each plant to allow 

 for the increase in growth. 



In order to determine the increase in leaf area from the time of inocu- 

 lation to the time of cessation of the experiment, the following method 

 was employed. By means of an adjustable glass plate and a tungsten 

 light, prints were made on contrast paper (Cyko) of each leaf on every 

 plant. These were developed and fixed in the usual manner. This was 

 done just before inoculation, and immediately after the last reading on 

 May 20th. By means of a planimeter, the area of the prints at various 

 periods was obtained. 



The disease was severe enough to cause the death of approximately 

 two-thirds of the tissue of every leaflet inoculated. The tabulated data 

 indicate the weighings and water added during the performance period 

 when no plants were inoculated, and the last six days when 11 of the 

 plants were infected. ^^ This gives the data as to the amount of trans- 

 piration from the time that infection was visible to the first signs of 

 general yellowing (break down) of the leaves. It is particularly neces- 

 sary to bear in mind this point since this experiment was concerned 

 only with the spots formed by the fungus and not with the secondary 

 yellowing of the leaf which follows infection. 



TABLE 4.— TRANSPIRATION OF HEALTHY AND DISEASED PLANTS: 

 WEIGHING PLANTS AND MEASURING LEAF SURFACE. 



TEST BY 



"At that time the Independence of moisture and infection was not known. 



"The detailed tables are given in Appendix, those given in the text being summaries. 



