[Vol. 2 



514 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



strated. He says that other factors, as, for example, the physi- 

 cal nature of the soil, decomposition of roots, change in re- 

 action of soil, etc., might be supposed to accomplish the same 

 results as toxic excretions from the roots. In pure distilled 

 water he found no decrease in either the size or quality of the 

 crops of the second and third plantings, either where wheat fol- 

 lowed wheat or where wheat followed oats. Experiments in 

 sand, however, showed great decrease in the amount of the 

 harvest of the second and third crops, but this, he believes, 

 might be explained by the operation of the above-named 



factors. 



So much for root excretions ; we now come to a general con- 

 sideration of exosmosis from living cells, both under natural 

 conditions and under treatment of different kinds. While a 

 great deal of attention has been given in the past to the in- 

 take, or endosmosis, of substances by the cell from its sur- 

 rounding medium, comparatively little has been done on the 

 opposite effect — the outgo, or exosmosis, of substances from 

 the cell. It should be said, however, that the latter process, 

 both in extent and in importance, is no doubt of much less 

 significance in the plant's economy than the former. 



Sachs ( '60 a ) referred to the exosmosis of soluble material 

 from germinating seeds when they remain for some time in 

 distilled water. Knop ('64), in his studies on the absorption 

 of salts by healthy seeds, also determined the quantities of 

 the different salts which pass out of the seeds during the time 

 they are swelling in distilled water. He found that both or- 

 ganic and inorganic substances were excreted. Hofmeister 

 ('67) ascertained that when fresh pieces of sugar-containing 

 plants were placed in water, no sugar passed out of the tis- 

 sues into the medium. The much-cited experiments of De 

 Vries ( '71) showed that pieces of red beet placed in water for 

 15 days gave no trace of sugar or of colored material to the 

 water during that time. In a NaCl solution of sufficient con- 

 centration, however, he obtained an exosmosis of both sugar 

 and colored material. Turnips, beets, and the seedling roots 

 of wheat, barley, and corn were used in the experiments of 

 Boussingault ( 74) but from none of them did he detect any 



