THE WILTTNO COEFFICIENT FOR PLANTS IN ALKALI SOILS. 



21 



of the soil mass, the glasses were kept in a partitioned metal tank, 

 through which a stream of water was kept flowing during the 

 whole period of the experiment. 1 A light tent of bolting cloth was 

 stretched over the tank during hours of bright sunlight, in order to 

 prevent, if possible, the heating and melting of the wax seals. 2 



EMERGENCE OF THE PLANTS. 



A record was kept of the rate at which the plants in each glass 

 appeared above the surface of the soil, this record having been based 

 on daily observations during the first 12 days (with the exception of 

 the eighth day after planting) and a final observation on the four- 

 teenth day, after which no more plants emerged. In mixture No. 15 

 no plants appeared. 



Table III shows the total number of plants (out of the 30 inserted) 

 which finally appeared above the seal and the number of days from 

 the date of planting to that when the last plant emerged in each soil 

 mixture. 



The behavior of the plants in the several glasses of the more con- 

 centrated soils (Nos. 11 to 14) was decidedly puzzling. In mixture 

 No. 11 all plants emerged in five of the glasses and none in the sixth. 

 In mixture No. 12 all plants emerged in three of the glasses and none 

 in the other three. In mixture No. 13 all plants emerged in three of 

 the glasses, all but one of the plants in two others, and none in the 

 sixth. In mixture No. 14 all plants emerged in two of the glasses 

 and none in the other four. No explanation could be found for these 

 irregularities. Electrolytic bridge readings at the close of the experi- 

 ment showed that they could not be attributed to differences in salt 

 content of the soil as between the glasses in which growth was made 

 and those in which no plants emerged. 



1 This method is described and illustrated in Bulletin 230, Bureau of Plant Industry, p. 13. 



2 In spite of these precautions, owing to the rather high temperatures that prevailed during the period 

 of this experiment , some softening and buckling took place in several of the glasses, which made it neces- 

 sary to break the seals in order to release plants caught beneath them. The seals were repaired so quickly 

 that no appreciable loss of water by direct evaporation could take place. This could have been obviated 

 by using for the seals a composition having a higher melting point. 



rrtr mm 



