54 DEPARTMENTAL REPORTS. 



PLANT LIFE HISTORY. 



Studies of the life histories of the principal crop plants are being 

 carried on to determine the exact environmental conditions necessary 

 to each stage of growth, and although the researches in this line are 

 still in their infancy, they have already yielded results of the highest 

 importance to agriculture. The work consists in a thorough investi- 

 gation of the exact requirements of climate and soil necessary to suc- 

 cessful growth and profitable production, and is similar to that done on 

 the date palm and set forth in the last Yearbook. It was not known 

 why the date palm was unfruitful in Florida and in parts of Cali- 

 fornia until our work demonstrated that a certain maximum amount 

 of heat is necessary to the production and maturation of fruit. As a 

 result of our studies in connection with this plant the areas where 

 it will thrive have been mapped, and include large tracts that are 

 now desert lands. It is known that much of the alkali desert land in 

 Arizona and in that general region can be reclaimed at compara- 

 tively slight expense by establishing a rotation of alkali-resistant and 

 heat-loving crops, with the date palm as a basis, as has been done in 

 the oases of the Sahara Desert. Similar studies are in progress in 

 connection with other crops and with the microscopic nitrogen gath- 

 erers of the soil, especially those that develop in connection with the 

 clovers and other Leguminosse. Other nitrogen-fixing microorgan- 

 isms that give great promise of economic importance have been dis- 

 covered. This work will receive special attention the current year. 



Fixation of atmospheric nitrogen. — Special attention is being given 

 to the whole subject of assimilation of atmospheric nitrogen by bac- 

 teria and other microorganisms, and in this connection a careful study 

 is being made of the life history of the bacteria which inhabit the root 

 tubercles of leguminous plants, and also of the plants themselves, with 

 a view of finding a means of favoring the process and of better util- 

 izing the nitrogenous matter^ thus formed in agricultural practices. 

 Pure cultures have been made of many of the principal races of these 

 bacteria, and we are endeavoring to find forms specially adapted to par- 

 ticular conditions of soil and climate. Such cultures, when obtained, 

 are to be distributed to the experiment stations for use in artificial 

 inoculation of soils on which new leguminous crops are grown. It is 

 often the case that the most effective bacteria are wanting on soils on 

 which such crops are being grown for the first time, and consequently 

 no fixation of atmospheric nitrogen results unless the proper bacteria 

 are introduced along with the new crop. 



The life histories of the principal leguminous plants are being 

 worked out, as before stated, in order to determine exactly the 

 regions to which they are best adapted, so that the best system of crop 

 rotations can be arranged and the best nitrogen-fixing plants for the 

 various regions determined. It is our intention to give particular atten- 

 tion to the finding of new leguminous crops which will fix nitrogen 

 abundantly for regions now lacking such plants or verj' poorly supplied, 

 and we hope through this work to reduce the outlay necessary for the 

 purchase of the very expensive nitrogenous manures and prevent 

 deterioration of soils where no manure is applied. Comparative 

 studies of the physiological and chemical action of the principal nitrog- 

 enous manures in comparison with the effects induced by preceding 

 leguminous crops are also contemplated. Besides the bacteria above 

 discussed, studies are being made of other soil bacteria which fix 



