14 ABSORPTION AND EXCRETION OF SALTS BY ROOTS. 
5 centimeters, but before any laterals had appeared. By very care- 
fully removing the seed coats, it was found that sterile cultures could 
always be obtained, for the fungi and bacteria which sometimes attack 
the cotyledons generally appear first as saprophytes on the dead 
tissue of the seed coats, from which they infect the cotyledons. Four 
seedlings were placed in each beaker, after washing them twice with 
distilled water. The culture solutions were all made up to a volume | 
Fic. 5.—Seedlings of culture 11, experiment C. 
of 500 c. c., so that an air space of 20 c. c. was left between the solution 
and the paraffin cake. When conductivity readings were made dur- 
ing the course of an experiment the culture solution was poured out 
through the hole at the side of the paraffin partition, and made up 
to 500 c. c. in order to replace the water lost by transpiration and 
evaporation. After determining its conductivity it was replaced 
without in the least disturbing the seedlings. The cultures were all 
kept in a dark chamber at laboratory temperature. 
231 
