BOTANY, 



ARABLE AND FOREST LAND OF THE UNITED STATES. 



UXDER the direction of the Smithsonian Institute, a map has been con- 

 structed, designed to represent at one view the extent and location of the 

 arable and forest land of the United States. The work has been intrusted 

 to Dr. J. G. Cooper, a naturalist, who has been engaged in government ex- 

 plorations in the western part of the United States, and who has critically 

 examined all the authorities to be found on the subject. The facts presented 

 at once to the eye by this map, are in striking accordance with the deduc- 

 tions from the meteorological materials which have been collected by the 

 Institution, and serve to place in a clear point of view the connection of cli- 

 mate with the natural productions of different parts of the earth Smith- 

 sonian Report for 1858. 



NEW GENERA OF AMERICAN PLANTS. 



At a recent meeting of the Boston Society of Natural History, Dr. Gray 

 presented specimens of a new genera of rosaceous plants, Neviusia Alaba- 

 mensis (Gray), recently discovered in Alabama by Rev. Mr. Nevins. 



That a new genus of plants should be detected at this late day, and that 

 one a large, ornamental, conspicuous shrub, is certainly rather surprising in 

 so well explored a locality. 



THE ABSENCE OF TREES FROM PRAIRIES. BY D. YAUGHAN. 



Ill tracing the influence of the several causes which are concerned in giv- 

 ing plants their geographical position, a very decided part must be ascribed 

 to certain meteoric conditions, which have hitherto received little attention. 

 The health and longevity of trees depend, in a high degree, on the manner 

 in which they are invigorated by seasonable supplies of rain during every 

 period of their growth; while the long droughts to which they are exposed 

 in many localities are productive of diseases which may cause the forest to 

 lose the dominion of the land. The extermination of trees on many vast 

 plains, is generally regarded as the work of man ; but, on a more careful 

 investigation, the phenomenon seems to correspond to what may arise from 

 the agency of unassisted nature. 



The fall of rain on different parts of the earth's surface depends not only 

 on their latitude and the proximity to large bodies of water, but also on the 



