216 BACTERIA. [CH. VIII 



acid within half-a-minute from the beginning of the 

 experiment. 



(249 a) Chemotaxis : Bacteria^. 



Allow a boiled pea to decay in about 200 cc. of water 

 for two or three days : draw off some of the fluid from just 

 below the surface, transfer a drop to a slide and place on 

 it a small cover-glass raised on two strips of paper. 

 Capillary tubes, like those used in exp. 249, are made by 

 drawing out coarse tubes in the blowpipe flame and again 

 drawing out the tubes so made over a small flame. 

 Lengths (10 mm.) of the fine capillary tubes should be 

 sealed, each at one end, and filled with 2 p.c. KNO3 under 

 the air-pump. They may be removed from the beaker of 

 KNO3 with a camel-hair paint-brush, and should be 

 examined under the microscope to make sure that they are 

 full. Having been washed with a drop of distilled water 

 they should be pushed under the cover-glass. In about 

 10 minutes the open ends ought to be crowded with 

 Bacteria. 



(249 b) Chemotaxis : pollen tubes'^. 



This may be easily demonstrated with the wild 

 hyacinth (Scilla nutans). A thin jelly is made by adding 

 3 p.c. of good gelatine (for instance the " bacteriological " 

 gelatine sold by Baird and Tatlock) to water and warming 

 over a water-bath. A large drop is placed on a slide and 



1 Pfeffer, Untersuchungen aus dem hot. Institut zu Tubingen, 11. 1888, 

 p. 582. 



2 Moliseh, Sitzb. d. k. AJcad. d. Wiss. in Wien^ ii. 1893 ; and 

 Miyoshi, Flora, 1894, p. 76. 



