BOTANY. 339 



THE EFFECT OF COLORED LIGHT ON GERMINATION. 



To determine the commercial value of any seeds, one hundred of them 

 are placed in a pot in a stove, made for the purpose of quickening the pro- 

 cess of germination. If all the seeds germinate, the seed obtains the high- 

 est value in the market. If only eighty germinate, the seed loses 20 per 

 cent, in value. This process ordinarily occupies from twelve to fifteen 

 days ; but Mr. Lawson found that by using blue glass they are enabled to 

 determine the value of seed in two or three days : and this is a matter of 

 such commercial importance to them that it is quite equal to a gift of 500 

 a year. Proceedings of the Royal Polytechnic Society. 



NEW AMERICAN GUM. 



The Washington Union, Nov. 9, 1854, contains the correspondence be- 

 tween Thomas S. Drew, superintendent of Indian affairs, and others, 

 relative to a recent discovery, which bids fair to be of great importance. 

 Dr. G. G. Shumard, physician and geologist to the Lake Expedition, 

 commanded by Captain Marcy, U. S. A., to the regions of the source of the 

 Big Wachita and Brazos Rivers, in the north of Texas, has discovered a 

 substitute for gum arabic, which he calls " gum mezquite," and which, 

 he has no doubt, will prove a valuable source of revenue to the States of 

 Texas, New Mexico, &c. 



In a letter from Dr. S. to Mr. Drew from Fort Smith, he says : 

 I comply with your request to furnish, for the use of the Indian de- 

 partment, a short description of the gum mezquite, discovered during our 

 recent expedition to the head waters of the Big Wachita and Brazos Rivers. 

 This gum, for which I propose the name of gum mezquite, is believed 

 to occur in inexhaustible quantities, and will, no doubt, prove a valuable 

 source of revenue to the States of Texas, New Mexico, and the adjacent 

 Indian territory, besides affording employment to the different tribes of In- 

 dians now roving upon the plains, many of whom would, no doubt, be 

 glad to gather and deliver it to the different frontier posts for a very small 

 compensation. 



The mezquite tree, from which this gum is obtained, is by far the most 

 abundant tree of the plains, covering thousands of miles of the surface, 

 and always flourishing most luxuriantly in elevated and dry regions. The 

 gum exudes spontaneously, in a semi-fluid state, from the bark of the 

 trunk and branches, and soon hardens by exposure to the atmosphere, 

 forming more or less rounded and variously- colored masses, weighing each 

 from a few grains to several ounces. These soon bleach and whiten upon 

 exposure to the light of the sun, finally becoming nearly colorless, semi- 

 transparent, and often filled with minute fissures. Specimens collected 

 from the trunks of the trees were generally found to be less pure and 

 more highly colored than when obtained from the branches. 



