TUBGIDITY 69 



trates, to some extent at least. Whether the effect be the 

 death of the plant or only an alteration in its metabolic 

 processes makes no difference for the present consideration.' 



e) Test by accumulation. — The power of penetration of all 

 inorganic salts, and of many organic compounds also, may 

 be tested by analysis of plant material which has been 

 grown in the solution to be tested. The various metallic 

 ions such as K, Na, Ca, etc., are known to accumulate ia the 

 bodies of higher plants. In this manner Bourget^ demon- 

 strated a marked absorption of iodin by various plant roots. 

 There is a great difference in different plants in this regard, 

 however; the Liliaceae and Chenopodiaceae absorb com- 

 paratively large quantities of iodin, while Solanum tuberosum, 

 grown in the same soil, fails to absorb enough for a test. 



Great accumulation of copper in plant cells has been 

 recorded several times. Thus, MacDougal ' describes a case 

 where a tree of Quercus macrocarpa absorbed copper in 

 large amounts and caused its precipitation within the wood 

 in the metallic state. 



All these accumulations come about by a chemical change 

 taking place in the substance after it has entered the cell, 



1 The following references will be of use to supplement those already given : F. 

 DE F. Heald, " On the Toxic Effect of Dilute Solutions of Acids and Salts upon 

 Plants," Bot. Gaz.,\ol. XXII (1896), pp. 125-53; H. M. Kiohaeds, "Die Beeinflussnng 

 des Wachsthums einiger Pilzedurch chemische Reize," Jahrb.f,wiss.Bot.,Vol.'KlX. 

 (1897), pp. 665-79; F. L. Stevens, "The Effect of Aqueous Solutions upon the Ger- 

 mination of Fungus Spores," Bot. Gaz.,Yol. XXVI (1898), pp. 377-406 ; E. B. Copeland 

 AND L. Kahlenbeeg, " The Influence of the Presence of Pure Metals upon Plants," 

 Trans. Wisconsin Acad. Sci. Arts and Let, Vol. XII (1899), pp. 454-74; N. Ono, 

 " Ueber die Waohsthumsbeschleunigung einiger Algen und Pilze durch chemische 

 Eeize," Jour. Coll. Sci. Imp. Univ. Tokyo, Vol. XIII (1900), reviewed in Bot. Gaz., 

 Vol. yxy (1900), p. 422; H. De Vaux, " De I'absorption des poisons mfitalliques tr6s 

 dilufe par les cellules v6g6tales," Compt. rend.. Vol. CXXXII (1901), pp. 717-20. 



2 P. BouEGET, " Sur I'absorption de I'iode par les v6g6teaux," Compt. rend.,No\. 

 CXXIX (1899), pp. 768-70; idem, same title. Bull. soc. chim. Paris, Ser. 3, Vol. XXIU 

 (1899), pp. 40-41. 



3D. T. MAcDonGAL, " Copper in Plants," J5oi. Gaz., Vol. XXVII (1899), p. 68. He 

 cites the following on the same general subject : Lehman, "Der Kupfergehalt von 

 Pflanzen und Thieren in knpferreichen Gegeuden," Arch. f. Hygien, Vol. XXVII 

 (1896), p. 1; J. B. Skeetschlt, "Tin Mines of Watsonville," Report Geologist 

 Queenslajid, 1897. 



