1894. ] Anatomical and Physiological Researches. 293 
Atkinson has suggested that the influence of the macro- 
symbiont upon the tubercle organism may have much to do 
with the variability of form as seen in the different types of 
bacteroids. 
Bearing upon this question of variety of species are the very 
interesting observations of Bolley?® on the natural distribu- 
tion of tubercles on the roots of indigenous and introduced 
legumes of the western plains. The native flora of the region 
is distinctively leguminous and he gives a list of native forms 
that he finds well provided with tubercles under natural con- 
ditions of environment. Many of the introduced legumes, es- 
pecially Trifolium pratense often fail to establish themselves in 
the Dakotas forsome reason. On stray plants, self-seeded and 
alone, he finds few, if any, tubercles, even though they may 
be growing in the midst of the native leguminous forms, but 
when preceded by 7. repens this form develops nodules on 
its roots and is apparently thrifty. Several other introduced 
aie fail to produce tubercles when planted on the virgin 
soil. 
The inability of these species to produce nodular outgrowths 
would seem to favor the theory that their special organism 
was lacking and therefore would indicate that there is a vari- 
ety of species. These observations have, however, only a 
circumstantial value in lieu of actual infection experiments. — 
H. L. Russe xt. 
The influence of traction upon the growth of plants. 
Hegler in a recent paper! points out some of the work 
done on this subject by other investigators: (1). Baranetzky 
concluded that the duration and intensity of growth were in 
no wise affected by traction. (2). Max Scholtz thought that 
the effect of traction was twofold: (a) a retardation which he 
Considered a pathological effect; (6) an acceleration in which 
€ Saw the real mechanical effect of the traction. The 
author advances some important objections to these conclu- 
‘tons and then gives an account of his own investigations. 
Method.—Two plants were used, one with and one with- 
Cut a weight. Measurements were taken by means of dis- 
tance marks, microscope and micrometer, or by the Bara- 
76 Ag. Science 7: 58 1 ee 
therein Rosen® Ueber den Einfluss des mechanischen Zugs auf das 
er Pflanze. Beitrage zur Biologie der Pflanzen, 6: 281. 1894. 
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