appearance of Torulse or other fungoid growths. Numerous live 

 aphides are found on the younger parts of the plant. 



Experiment No. 2. — May 13. — A small geranium plant (Pelar- 

 gonium a?igulosuin var.^, infested with a considerable number of 

 aphides, is sprinkled with domestic yeast (the same as in No. i), 

 and placed in a window in its ordinary position among other 

 plants not infested. 



May 15. — Aphides more scattered but apparently not less in 

 number. 



May 18. — Aphides plainly more numerous. Numbers of cast- 

 off skins from molting. Some leaves of geranium with dark- 

 brown spots obviously caused by drops of yeast ; other plants of 

 the same kind not treated with yeast show no spots. 



June 3. — Aphides numerous and healthy. Quantities of cast- 

 off skins. No dead aphides to be found. Foliage obviously 

 injured by the yeast. Plant plainly enfeebled by the aphides. 



Experiment No. 3. — May 10. — A calla lily has become infested 

 with aphides and red spider. The whole plant is carefully washed 

 with a sponge except a small spot on one leaf where twenty-seven 

 aphides are left, and a similar spot on another leaf where about 

 twenty red spiders are left. The whole plant is sprinkled with 

 domestic yeast, care being taken to thoroughly drench both the 

 aphides and red spiders. The plant is covered by a bell jar which 

 rests upon a ring of cotton batting, so as to shut the plant off 

 from the approach of insects or spores from without, and prevent 

 the escape of those within. Under the bell jar are placed two cups 

 of actively fermenting yeast. 



May 14. — The plant carefully examined. No dead aphides to 

 be found. A number of cast-off skins are seen. The aphides 

 are well scattered over the plant, but more than the original twenty- 

 seven can be counted. The red spiders are also scattered so that 

 the number cannot be ascertained. Several living but no dead 

 ones are seen. That the spiders should have decreased in num- 

 bers might be expected from the moisture of the yeast independent 

 of the Torulae. 



Experiment No. 4. — April 8. — Selected a thrifty rose geranium, 

 about ten inches high, that had by count seventy aphides upon 

 it, collected mainly upon the tender shoots. 



The yeast is prepared by dropping pieces of compressed yeast- 

 cake, bought at the grocer's, into Pasteur's fluid with sugar. In 



