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Show 518 MODIFIED CIRCUMNUTATION. C!IA!'. X. tho prost:ato habit o.f JTelianthemum p?"08t?·atnm "brings tho cap.sules m .contact w1th tho surface of tho ground, postpones their matunty, and so favours tho seeds attaining a larger size." ~he capsule~ of Cyclmn.on and of Oxalis (/cetosdla arc only occasiOnally buried, and this only beneath dead lcaveR or moss. If it be an advantngo t.o a p!ant that its capsules should be kept damp and cool by bomg lmcl on tho ground, we b:we in these latter cases tho first step, from which tho power of penetrating the ground, with tho aid of tho always present movement of circumnutation, might afterwards have been gained. Arachis hypogrea.-The flowers which bury themselves, rise from stiff branches a few inches above tho ground, and stand upright. After they have fallen off, tbe gynophore, that is the part which supports the ovarium, grows to a great length, even to 3 or 4 inches, and bends perpendicularly downwards. It resembles closely a peduncle, but has a smooth and pointed apex, which contains tho ovules, and is at first not in the least enlarged. Tbe apex after roaching tho groun<l penetrates it, in one case observed by us to a depth of 1 inch, and in another to 0·7 inch. It there becomes developed into a largo pod. Flowers which are seated too high on the plant for tho gyno· phore to reach the ground arc said* never to produce pods. The movement of a young gynophore, rather under an inch in length and vertically dependent, was traced during 46 h. by means of a glass filament (with sights) fixed transversely a little above tho apex. It plainly r.ircumnutatcd (Fig. 193) whilst increasing in length and growing downwards. It was then raised up, so as to be extended almost horizontally, and the terminal part curved itself downwards, following a nearly straight course during 12 h., but with one attempt to circumnutate, as shown in Fig. 194. After 24 h. it had become nearly vertical. Whether the exciting cause of tho downward movemont is geotropism or apheliotropism was not ascertained; but probably it is not apheliotropism, as all the gynophores grew straight down towards the ground, whilst the light in the bot- 1\ouse entered from one side ns well as from above. Another and older gynophore, tho apex of which had nearly reached the ground, was observed during 3 days in tho same manner .as the first-mentioned short one· and it was found to be always Circumnutating. During the :fi~·st 34 h. it described a figure which * 'Garu. Chronicle,' 1857, p. 5G6. CHAP. X. GEOTROPISM. 51D represented four ellipses. Lastly, a long gynophore, the apex of which had buried itself to the depth of about half an inch, was Fig. Hl3. '',,'\. '" '\.. ', 4 // /l/ #" //! ,/'/ Arachis hypogce'l: circumnutation of vertically dependent young gynophore, traced on a. vei'tical glass from 1 0 A.M. July 31st to 8 .A.M. Aug. 2nd. Fig. 194. Arachis hypogrea: downward movement of same young gynophore, after being extended horizontally; traced on a vertical glass from 8.30 A.M. to 8.30 P.M • .Aug. 2nd. ~ulied up a~d extended horizontally: it quickly began to curve ownwards m a zigzag line; but on the following day tho tor- |