It is possible that some secondary radicles are more sensitive than others; for Sachs has proved[5] the interesting fact that each individual secondary radicle possesses its own peculiar constitution. [4] ‘Arbeiten Bot. Inst., Würzburg,’ Heft iv. 1874, p. 605–617. [5] ‘Arbeiten Bot. Instit., Würzburg,’ Heft, iv. 1874, p. 620. Sensitiveness to contact of the Primary Radicle, a little above the apex, in the Bean (Vicia faba) and Pea (Pisum sativum).—The sensitiveness of the apex of the radicle in the previously described cases, and the consequent curvature of the upper part from the touching object or other source of irritation, is the more remarkable, because Sachs[6] has shown that pressure at the distance of a few millimeters above the apex causes the radicle to bend, like a tendril, towards the touching object. By fixing pins so that they pressed against the radicles of beans suspended vertically in damp air, we saw this kind of curvature; but rubbing the part with a twig or needle for a few minutes produced no effect. Haberlandt remarks,[7] that these radicles in breaking through the seed-coats often rub and press against the ruptured edges, and consequently bend round them. As little squares of the card-like paper affixed with shellac to the tips were highly efficient in causing the radicles to bend away from them, similar pieces (of about 1/20th inch square, or rather less) were attached in the same manner to one side of the radicle at a distance of 3 or 4 mm. above the apex. In our first trial on 15 radicles no effect was produced. In a second trial on the same number, three became abruptly curved (but only one strongly) towards the card within 24 h. From these cases we may infer that the pressure from a bit of card affixed with shellac to one side above the apex, is hardly a sufficient irritant; but that it occasionally causes the radicle to bend like a tendril towards this side. [6] Ibid. Heft iii. 1873, p. 437. [7] ‘Die Schutzeinrichtungen der Keimpflanze,’ 1877, p. 25.