THE AMERICAN BOTANIST 



107 



ient for our needs. It used to be thougdit that all soils needed 

 to be supplied with potassium, but a recent publication of the 

 University of Illinois asserts that in ordinary soil the supply 

 of potash is practically inexhaustible ; in fact, that a square 

 mile of corn-belt land six feet deep contains more potash than 

 is applied annually to all the farms in the United States. In 

 a single acre, as deep as the plow goes, there are 35,000 pounds 

 of potassium. Analysis of farm crops have shown a potash 

 content that would indicate that a great amount of this sub- 

 stance is needed, but it now appears that plants usually take up 

 more than is necessary for growth. ^luch of the potash in 

 soils, however, is not weathered out in a form available for 

 plants, but by incorporating with the soil vegetable matter of 

 an}^ kind, the material is made available. All that the farmer 

 needs to do, therefore, is to plow under stable refuse and he 

 may read the war news without uneasiness so far as its effect 

 on the fertility of his soil is concerned. 



Obedient Plant. — One of the characteristic plants of 

 prairie regions is a pink-flowered member of the mint family 

 which botanists know as Physostcgia Virginica. It is suffic- 

 iently attractive to be given a place in the flower garden and 

 most nurserymen oft'er it under the common name of obedient 

 plant. This name does not seem to have gotten into the botan- 

 ical books however, for they still list it as lion's heart, or false 

 dragon-head. These names are apparently seldom if ever 

 used. The nurseryman's name is more descriptive, though it 

 is possible that many who are familiar with the plant may be 

 at a loss to understand hoAV it applies. For the beneflt of such 

 it may be said that Avhen the plant is in bloom, one may push 

 the individual flowers of a spike about in various directions 

 and they will obediently remain where placed until put in a new 

 position. AMien the flowers of other plants are pushed about 

 in this way they at once spring back into place as soon as the 

 pressure is released, but the pedicels of the obedient plant are 



