87 
winter to five or six times less in the summer. Forest soil en- 
courages sap bacteria and no pathological bacteria are found in it. 
Roth (For. Cond. and Int. of Wis. U. S. Dept. Agr. Div. of 
For. Bul. 16: 34. 1898) says: ‘“ Hemlock has a shallow system 
of roots, sensitive to the interference in soil moisture, hence 
furnishes a great quantity of dead and down material. Over 
wide areas only old trees occur, these often dying out. There is 
apparently no lack of seed, for the hemlock, like the pine this 
season (1897), was full of cones, and yet there is very little repro- 
duction of this timber. For miles no young growth is seen, and 
the small trees, often mistaken for saplings, generally prove to 
be runts, suppressed individuals, often 150 and more years old. 
The only places where this tree still seems to hold its own are in 
some of the wet half swamps of the eastern part of this area. 
The young hemlock stands a great deal of shading and close 
crowding, but grows slowly both in height and thickness.” 
We must look then to the hemlock seedlings which germinate 
in the open spaces in the grove, where deciduous trees and 
shrubs shelter them as they develop yet do not form too dense a 
cover, for the continuance of the hemlock grove. 
WINIFRED J. ROBINSON. 
SOME EAST INDIAN ECONOMIC PLANTS 
AND THEIR USES. 
Economic plants are those whose products, such as fibers, 
starches, and sugars, are utilized by mankind. Fibers are obtained 
from the bark, stems, and leaves of many plants and are made use 
of in various ways. Of the plants from whose leaves useful fibers 
are obtained, one of the commonest and most extensively utilized 
types is the group of the screw-pines, a genus of plants contain- 
ing over one hundred species, which are confined entirely to the 
eastern hemisphere, and a dozen or so to the islands of the Malay 
Archipelago and vicinity. The screw-pines derive their appella- 
tion not from any resemblance to the pine-family, but from the 
spiral growth of their leaves and the similarity of their foliage to 
that of the pineapple. Some species attain the size of trees, with 
