40 THE AMERICAN BOTANIST 



insectivorous sundews, pitcher plants and butterworts, the 

 cranberry and other heaths, various orchids, the cotton grass 

 and the peat mosses {Sphagnum.) Naturally such plants "are 

 difficult to manage in cultivation. They appear to miss their 

 acid soil and are especially intolerant of limestone. People in 

 limestone regions have usually had to deny themselves the 

 pleasure of growing such species and have therebv missed a 

 number of fine flowers, such as rhododendrons, kalmias, and 

 azalias. The trailing arbutus and blueberry are other heaths 

 that have thus far resisted practically all efiforts to cultivate 

 them in ordinary garden soil. The trailing arJuitus, especial- 

 ly, has the reputatiort of being impossible to grow awav from 

 its native haunts. Some years ago, however, it was discov- 

 ered that this plant would grow in soils containing considerable 

 amounts of oak leaves and now Henry Bird has discovered 

 that in regard to the pitcher-plants, at least, a small amount 

 of tannic acid added to the soil, will reconcile the plants to 

 domestication. The acid is supplied by an extract of hemlock 

 bark in the [)roportion of one part of the acid to from tifty to 

 a hundred parts of water. It is at present unknown whether 

 other plants may be induced to grow by like treatment, but 

 from the fact that oak leaves aid thearbutus to thrive, it appears 

 likely that tannic acid, or perhaps other organic acids, nvAx be 

 all that is needed to promote the growth of acid soil plants un- 

 der garden conditions. The subject is one that otfers most 

 interesting opportunities for investigation b\- those who have 

 access to a small greenhouse. By setting up a series of potted 

 plants as nearly alike as possible, and watering them with di- 

 lute solutions of different acids, it would soon be apparent 

 whether a single acid can produce the effect, or whether sev- 

 eral '-ids have the jjower. To discover just vvhat acid will 



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