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Show 54 CIRCUMNUTATION OF SEEDLINGS. CHAP. I. the windows was 11 little more illuminated than the opposite side ; and during the first morning the st~m travelled to a greater distance in this direction (to the left m the figure) than it did afterwards when the box was completely protected from light. Qttercus (American sp.): circumnutation of young stem, traced on hori· zontal glass, from 12.50 P.M. Feb. 22nd to 12.50 P.M. 24th. Movement of bead greatly magnified at first, but slightly towards the close of the observations-about 10 times on an average. Que1·ws robuT.-Observations were made only on the movements of the radicles from germinating acorns, which were allowed to grow downwards in the manner previously described, over plates of smoked glass, inclined at angles between 65° and 69° to the horizon. In four cases the tracks left were almost straight, but the tips had pressed sometimes with more and sometimes with less force on the glass, as shown by the varying thickness of the tracks and by little bridges of soot left across them. In the fifth case the track was slightly serpentine, that is, the tip had moved a little from side to side. In the sixth case (Fig. 41, A) it was plainly serpentine, and the tip had pressed almost equably on the glass in its whole course. In the seventh case (B) the tip had moved both laterally 11nd bad prossed CHAP. I. QUERCUS AND CORYLUS. 55 alternately with unequal force on the glass; so that it had moved a little in two planes at right angles to one another. In the eighth and last case (C) it had moved very little laterttlly, but had alternately loft the glass and come into contact with it again. There can bo no doubt that in tho last four cases the radicle of the oak circumnutated whilst growing downwards. Fig. 41. \ A c Quercus 1·obur: tracks left on inclined smoked glass-plates by tips of rarlicles in growiug downwards. Plates A and C inclined at 6v0 and plate B at 68° to the horizon. Corylus avellana (Corylacere).-The epicotyl breaks through the ground in an arched form; but in the specimen which was first examined, the apex had become decayed, and the epicotyl grew to some distance through the soil, in a tortuous almost horizontal direction, like a root. In consequence of thi~ injury it had emitted near the hypogean cotyledons two secondary shoots, and it was remarkable that both of those were arched like the normal opicotyl in ordinary cases. The soil was removecl from around one of these arched secondary shoots, and a glass filament was affixed to the basal log. The whole was kept damp beneath a met11l-box with a glass lid, and was thus illuminated only from above. Owing apparently to the lateral pressure of the earth being removed, the tormina.l and bowed-down part ?f th~ shoot bega.n at onge t? move upwards, so that after 24 h. It formed 11 right angle with the lower part. This lower ~art, to which the filament was attached, also stmightened Itself, and moved a little backwards from the upper part. Consequently a long line was traced on the horizontal glass; and |