OCR Text |
Show 212 CIRCUl\INUTATION OF STEMS. CuAP. IY. (19.) Lili'mn at~ratum (Fam. Liliacero).-The circumnutation Fig. 83. .--··-----r-·---··- EJ'a.m.14th. Lilium auratum: circumnutation of a stem in darkness, traced on a h?rizontal glass, from 8 A.M. on March 14th to 8.35 A.M. on 16th. But 1t should be noted that our observations were interrupted between 6 P.llf. on the 14th and 12.15 P.M. on 15th, and the movements during this intel'l'al of 18 h. 15m. are representeu by a long broken line. Diagram reduced to half original scale. of the stem of a plant 24: inches in height is represented in the above figure (Fig. 83). Fig. 48. '11 . t d from above, Cuperus alternifolius: circumnutation of stem, 1 umma e lOth. traced on horizontal glass, from 9.45 A.M. March 9th ~0 9 P.llf.tO~ossiblc The stem grew so rapidly whilst being observed, that 1t was no I. to estimate how much its mo'V'ements were magnified in the traclllg. . . . )-A glass (20.) Oyperus alternifohus (Faro. Cyperacere. CHAP. IV. CIROUl\INUTATION OF STEl\IS. 213 filament, with a boacl at the cncl, was fixocl across the summit of a young stem 10 inches in height, close beneath tho crown of elongated leaves. On March 8th, between 12.20 ancl 7.20 P.M., the stem described an ellipse, open at one on<l. On tho following day a new tracing was begun (Fig. 81), which plainly shows that the stem completed three irregular figures in tho course of 35 h.l5 m. Concluding Remarks on the Circumn~dation of Stems.Any one who will inspect the diagrams now given, and will bear in mind the widely separated position of the plants described in the series, -remembering that we have good grounds for the belief that the hypocotyls and epicotyls of all seedlings circumnutn.te,-not forgetting the number of plants distributed in the most distinct families which climb by a similar movcment,- will probably admit that the growing stemf:i of all plants, if carefully observed, would be found to circumnutate to a greater or less extent. '\Vhen we treat of the sleep and other movements of plant~, many other cases of cireumnutating stems will be incidentally given. In lookino· at the dinoTnms we \.. b b ' should remember that the stems were always oTowin(Y b t:>' so that in each case the circumnutating apex as it rose will have described a spire of some kind. The dots were made on the glasses generally at intervals of an hour, or hour and a half, and wore then joinecl by straight lines. If they had boon made at intervals of 2 or 3 minutes, the lines would have been moFP curvilinear, as in the case of the tracks left on th<-J sm~ked glass-plates by the tips of the cireumuutating radiCles of seedling plants. The diagrams generally ~pproach in form to a succession of more or less ~~egular ellipses or ovals, with their longer axes lrected to different points of the compass during the same day or on succeeding days. The stems there- •" I''" :if:~ t ''"' :.,; ;; ~I |