110 EXPERIMENT STATION RECORD, 



mente of various autlions concerning the pos8il)ility of albmuin synthesis in tlie dark 

 by the higher j)lants. — v. fireman. 



Rheotropism of roots, F. C. Newcombe {Ahs. in Science, n. ser., 13 {1901), No. 

 320, p. 250). — Rheotropism is defined as the curvature of the root when growing in 

 running water. In all cases so far observed the root tip curves against the stream. 

 In the experiments upon which the report is based the author examined 32 species 

 of jilants, 15 of which have shown themselves to l^e rheotropic and 17 insensitive. 

 Species of the same genius differ widely in the degree of response to this stimulus. 

 Members of the Cruciferfe are among the most sensitive plants found, their roots 

 often attaining an angle of 90° from the vertical. The velocity of the current was 

 found to exercise a considerable influence upon the amount of curvature, the l^est 

 response being given in a current carrying from 100 to 500 cm. per minute. A 

 velocity of 2,000 cm. per minute in most plants produced a negative curve. The 

 area of the root which perceives the stimulus includes the apex of the root and the 

 elongating Z(jne, and the roots of mature plants are as responsive as those of seedlings. 



Thigmotropism of roots, F. C. Newcombe {A})^. in Science, n. ser., 13 {1901), No. 

 320, i)p. 250,251). — The sensitiveness of roots to contact or pressure has been investi- 

 gated and the author shows that roots are responsive to pressure on the elongating 

 zone. Some species respond to pressure while others do not, and the response is 

 considered of the same class of phenomena as shown by tendrils when in contact 

 with a solid object. In the experiments outlined by the author all the roots that 

 showed the effect of this stimulus became concave on the side receiving the stimulus. 



The relation of water plants to the solid substratum, R. H. Pond {Ahn. in 

 Science, n. ner., 13 {1901), No. 320, pp. 256, 257). — The common statement that the 

 roots of water plants serve only as means of attachment requires, according to the 

 author, some modification. He has found that aijuatic plants rooted in soil exc^eeded 

 in vegetation and dry weight plants rooted in sand or merely suspended. Plants 

 rooted in saml or merely suspended contained an excess of starch, lime, and magne- 

 sium, while they were lacking in nitrogen, potash, and phosphoric acid. A volu- 

 metric measurement of root absorption was made showing that the rooted plants 

 absorbed more than floating ones. 



The influence of the presence of pure metals upon plants, E. B. Copelanu 

 and L. Kahlenbekg ( Tra/t.s. Wisconsin Acad. Sd., Arts, and Letters, 12 {1900), pt. 2, 

 pp. 454-474)-— "^^Q authors state that injury to plants grown in cultures containing 

 pure metals will dei:)end ui>on the tendency of the metal to go into solution and 

 the specific toxicity of the metal when in solution. A series of experiments were 

 conducted in which chemically pure metals were placed in distilled water, and 

 the effect noted upon the growth of a number of plants. As many of the metals as 

 were available were rolled into foil or were in the shape of wire. Some of the other 

 metals were in the form of sticks, others in flakes, etc. The vessels containing the 

 water cultures were glass beakers, coated internally with paraffin, so that no solu- 

 tion of glass would be possible. Seedlings of maize, lupines, oats, and soy beans were 

 placed in these solutions and the effect of their growth determined by the increase 

 in length of the radicles. In all, 30 metals were tested, the more common of which 

 were copper, nickel, tin, silver, platinum, gold, mercury, antimony, bismuth, cobalt, 

 iron, zinc, lead, manganese, sulphur, and carbon. The effect of these different ele- 

 ments is shown in tabular form. It appears that thallium, cadmium, copper, cobalt, 

 zinc, lead, iron, antimony, magnesium, arsenic, iodin, tungsten, and tellurium were 

 almost invariably fatal to the growth of plants. It was not always possible to dem- 

 onstrate by chemical tests the presence of these substances in the roots which they had 

 killed, but in a number of instances the appearance of the roots showed the presence 

 of the salts of the metal that had killed it. It was found that those metals whose 

 salts are already known to be toxic poisoned plants when present in water. It is 

 stated as a well-recognized fact in animal physiology that the i)henomena of stimu- 



