78 THE AMERICAN BOTANIST 



ground. Moreover, a cutting taken from an old plant ought to 

 bloom sooner than a similar plant from seed. The horticultur- 

 ist sometimes hastens the fruiting of a young tree by grafting 

 a twig from some older tree upon it. It would seem, then, 

 that a layer from Wisteria should bloom sooner than a seed- 

 ling, but that the position in which it grows has considerable 

 effect. 



Fertility of the Soil. — At first glance the fertility of 

 the soil does not seem to lie in the province of the botanist, but 

 the further investigation is pushed in this direction, the more 

 does it appear to be entirely botanical notwithstanding all the 

 fertilizers that the farmers still considers essential. There are 

 certain chemical elements necessary to any fertile soil, to be 

 sure, but given these no crops will grow without nitrates or 

 nitrogen in some form and since nitrogen does not exist natur- 

 ally in the soil, the supply must result from the action of bac- 

 teria. There is a large class of plants known as legumes, of 

 which the pea and bean are examples, which have formed part- 

 nerships with certain bacteria able to fix atmospheric nitrogen, 

 but the nitrogen used by other plants comes from the oxida- 

 tion of ammonia and other organic compounds of nitrogen ad- 

 ded to the soil. This oxidation is caused by bacteria, which, 

 most people do not need to be told, are plants. But even these 

 atoms have their enemies which must be overcome before they 

 can do their best work. It has recently been discovered that 

 there are immense numbers of one-celled, microscopic animals 

 known as protozoa in the soil and these spend their time de- 

 vouring the helpful bacteria. The problem is to make away 

 with these harmful protozoa. Experiment has proven that 

 this can be accomplished by baking the soil, pouring boiling 

 water upon it, or even by treating it with chloroform or car- 

 bon disulphide. Most of the protozoa are killed by these pro- 

 cesses and large numbers of the bacteria also, but the latter 

 soon increase again and then number seven or eight times as 



