^00 THE PLANT WORLD. 



brought in doors and tied up in a few minutes. If hung over a stove 

 or camp-fire they get quite as warm as if placed in the sun. For a 

 country where there is not much wind, gummed paper clasps, sold by 

 all stationers, may be fastened at the end. These are quite inexpen- 

 sive and quickly put on. Any one who tries this method will never 

 go back to the old method of spreading out the driers. I travel by 

 rail usually and carry about 500 driers with me. It would require 

 considerable space for this number to be spread out, and instead of 

 appropriating two or three back lots, I now want only a few feet of 

 space where there is plenty of sunshine and air. 



Instructor in Science, High School, Denver. Colorado. 



PLANT JUICES AND THEIR COMMERCIAL VALUES. 



By Mrs. Caroline A. Crccvcy. 



[continued.] 



ONE of the most useful articles known to man is the elastic sub- 

 stance, India rubber. This is obtained from the milky juice 

 of many plants — of the Spurge, Bread-fruit, Mulberry and 

 Dogbane families. The Para rubber heads the list in value, 

 being the product of Hevca Braziliensis^ growing often 100 feet 

 high, a tree of the Spurge family, found abundantly in the regions of 

 the Amazon and on islands of that mighty river. The native Indians 

 collect the milky juice after the floods subside, from August to Feb- 

 ruary. Deep incisions are made into the tree, both vertical and 

 slanting, from which the juice, flowing, is caught in small cups fast- 

 ened to the tree by lumps of moist clay. Each tree yields about 

 two ounces a day. Soon after coming to the air the juice thickens 

 and becomes like paste. Ammonia, which is mixed with it, quickly 

 evaporates, and more must be added to keep it from coagulating if it 

 has to be carried any distance. To prepare it for market the natives 

 pour it in thin layers on shovels or clay moulds, and hold it, often 

 turning it, over a slow fire, made, if possible, from the oily nuts of 

 certain palms. After the first layer is dry a second is added, a third, 

 and others, till a sufficient thickness is produced. The whole is then 

 cut around with a sharp knife, slipped off the mould and hung up to 

 dry. In the trade these are called rubber biscuits, and are about eight 

 inches thick. 



Eighteen genera and forty-four species of trees are now known 

 to yield good rubber. Next to the Para is the Ceara rubber, also a 

 Euphorbia, found in the province of Rio Janeiro. From this tree the 



