interval of 5 h. 30 m.; and we merely record in our notes “almost all bent slightly from the perpendicular, and away from the squares; the deflection amounting in one or two instances to nearly a rectangle.”  These two sets of cases, especially the first one, prove that the apex of the radicle is sensitive to slight contact and that the upper part bends from the touching object.  Nevertheless, on June 1st and 4th, 8 other radicles were tried in the same manner at a temperature of 58o — 60o F., and after 24 h. only 1 was decidedly bent from the card, 4 slightly, 2 doubtfully, and 1 not in the least.  The amount of curvature was unaccountably small; but all the radicles which were at all bent, were bent away from the cards.

We now tried the effects of widely different temperatures on the sensitiveness of these radicles with squares [page 160] of card attached to their tips.  Firstly, 13 peas, most of them having very short and young radicles, were placed in an ice-box, in which the temperature rose during three days from 44o to 47o F. They grew slowly, but 10 out of the 13 became in the course of the three days very slightly curved from the squares; the other 3 were not affected; so that this temperature was too low for any high degree of sensitiveness or for much movement.  Jars with 13 other radicles were next placed on a chimney-piece, where they were subjected to a temperature of between 68o and 72o F., and after 24 h., 4 were conspicuously curved from the cards, 2 slightly, and 7 not at all; so that this temperature was rather too high.  Lastly 12 radicles were subjected to a temperature varying between 72o and 85o F., and none of them were in the least affected by the squares.  The above several trials, especially the first recorded one, indicate that the most favourable temperature for the sensitiveness of the radicle of the pea is about 60o F.

The tips of 6 vertically dependent radicles were touched once with dry caustic, in the manner described under Vicia faba.  After 24 h. four of them were bent from the side bearing a minute black mark; and the curvature increased in one case after 38 h., and in another case after 48 h., until the terminal part projected almost horizontally.  The two remaining radicles were not affected.

With radicles of the bean, when extended horizontally in damp air, geotropism always conquered the effects of the irritation caused by squares of card attached to the lower sides of their tips.  A similar experiment was tried on 13 radicles of the pea; the squares being attached with shellac, and the temperature between 58o — 60o F. The result was somewhat different; for [page 161] these radicles are either less strongly acted on by geotropism, or, what is more probable, are more sensitive to contact.  After a time geotropism always prevailed, but its action was often delayed; and in three instances there was a most curious struggle between geotropism and the irritation caused by the cards.  Four of the 13 radicles were a little curved downwards within 6 or 8 h., always reckoning from the time when the squares were first attached, and after 23 h. three of them pointed vertically downwards, and the fourth at an angle of 45o beneath the horizon.  These four radicles therefore did not seem