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Show 32 CIRCUMNUTATION OF SEEDLINGS. CHAP. I. two occasions during three days. But the tracings made under such unnatural conditions are not worth giving; and it need only be said that the lines were decidedly zigzag, and that small loops were occasionally formed. We may therefore conclude that the epicotyl circumnutates whilst still arched and before it has grown tall enough to break through tho surface of the ground. In order to observe the movements of the epicotyl at a some-what more advanced age, a filament was fixed near tho base of one which was no longer arched, for its upper half now formed a right angle with the lower half. This bean had germinated on bare damp sand, and the epicotyl began to straighten itself much sooner than would have occurred if it had been properly planted. The course pursued during 50 h. (from 9 A.M. Dec. 26th, to 11 A.M. 28th) is here shown (Fig. 22) ; and we sec Fig. 22. Vicia faba: circumnutation of young epicotyl, traced in darkness during 50 hours on a horizontal glass. Movement of bead of filament mag· nified 20 times, here reduced to one-half of original scale. that the epicotyl circumnutated during the whole time. Its basal part grew so much during the 50 h. that the filament at the end of our observations was attached at tho height of ·4 inch above the upper surface of the bean, instead of close to it. If the bean had been properly planted, this part of the epicoty l would still have been beneath the soil. Late in the evening of the 28th, some hours after the above observations were completed, the epicotyl had grown much straighter, for the upper part now formed a widely open angle with tho lower part. A filament was fixed to tho upright basal part, higher up than before, close beneath the lowest scale-like process or homologue of a leaf; and its movemeut was traced CHAP. I. LATIIYRUS. 33 rluri~g 381~. (Fig. 23). We hero again have plain evidence of contmu.ed cn·cumn~ltation. Had the bean been properly planted tho part of the opiCotyl to which tho filament was attached, th~ Fig. 23. Vicia faba · circum t t' f h ad yau c~ 1. uu_ a 10 11 0 t e .sa~1 e epicotyl as in Fig. 22, a lit t le more () 28 ( 1 111 age, tl aced under S1111llar conditions as before from 8 ..JO A M ec. t 1 to 10 50 A M 30th ' · · · 20 times. ' · · · · Movement of bead here magniJied n.JOvomont of which is here shown, would probably have juF>t l'ISon above tho surface of tho ground. La.thy~us ~issolia .<Leguminosre).-This plant was so1ectoc1 fur obs01 vatwn from bemg an abnormal form with grass-like Ieavefl. Fig. 2+. ---..... -~ Lut~y~~s nissolirt: cir~u mnutat i.m of ~tem of young seellling traced in ~I. ,ness on a hon zontal glass, fr om G.4!) A.l\f, Nov. 22n~J· to 7 11 M 2:hd. Movement d . ·' t of <>nd of leaf · r d b ' · · 1 . . magnwe a out 12 timeti here re-uceu o one- 1al f of ol'lgmal seale. ' ~l;ho rrc~tyled~ns arc h,vpog~an, and tho epicotyl breaks through . 10 o 1.ound. m an arc heel form. The movements of a stem 1·2 ~nch m hmght, comdsting of thl'eo internodes, tho lower 'ono a.lmost who11y subterra.noan, and tho upper one bearing a short, l l |
