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Show 158 SENSITIVENESS OF THE APEX CnAr. III. analoO'ous cases will be immediately dosoribo<l. 'fhe facti~ here mentioned because it was a striking spectacle, showing the difference in tho sensitiveness of the radicle in different parts, to b hold in tho same jar one set of radiclos curved away from the squares on their tips, an<l another set curved tm·vards tho squares attached a little higher up. Moreover, tho kind of curvature in tho two cases is different. The squares attached above the apex cause tho radicle to bend abruptly, the part above and beneath remaining nearly straight; so that here there is little or no tnmsmitted effect. On the other hand, tho squares attached to the apex affect the radicle for a length of from about 4 to even 8 mm., inducing in most cases a symmetrical curvature ; so that here some influence is transmitted from the apex for this distance alollg the radicle. Pisum sativum ( var. Yor!cshire Hero): Sensitiveness of the apex of the Radicle.-Littlo sqnares of the same card· like paper were affixed (April 24th) with shelbc to one side of the apex of 10 vertically suspended radicles: the temperature of the water in the bottom of the jars was 60°-61° F. 1\iost of these racliclcs were n,ctccl 011 in 8 h. 30m.; and eight of them became in the course of 24 h. conspicuously, and the remaining two slightly, deflected from the perpendicular and from tho side bearing the attached squares. 'rhus all were acted on; but it will suffice to describe two conspicuous cases. In one the terminal portion of the radicle 'vas bent at right angles (A, Fig. 66) after 24 h.; and in the other (B) it had by this time become hooked, with the apex pointing to the zenith. The two bits of card here used were ·07 inch in length and ·04 inch in breadth. Two other radicles, which after 8 h. 30 m. were moderately deflected, became straight again after 24 h. Another CHAP. III. OF THE RADICLE OF 'l'HE PEA. 159 trial was made in the same manner with 15 radicles; but from circumstances, not worth explaining, they were only once and briefly examined after the short Fig GG. A. n. Pisum s~tivum: deflection produced withiu 24 hours in the growth of vel'tiCally dependent ra<licles, by little squares of card nflixe<l with shellac to one side of apex: A, bent at 1·ight angles ; B, hooked. 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 amountincr 0 b m 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 slio·ht contact b an~ that the upper part bends from th touching obJect. Nevertheless, on Juno 1st and 4th 8 other radicles were tried in the same manner at a temperature of 58°-60° F., and after 24 h. only 1 was decidedly ?ent from the card, 4 slightly, 2 doubtfully, ancl 1 not m 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 tho effects of widely d.iffcrcnt temperatures on the sensitiveness of these radiclcs with squares ~.I:~; • :J~, ,t.::~; IWI·•f' li.l .. ; t::::J l ')•" 1-" : :;;~; ,:,, ,~ ,:,; ., ,,,,. : '' .I If II 111 ~ •• I · ~ Il l .• : ~: fl |