Both these leaves certainly circumnutated, making within the above period two, or two and a half, small, irregular ellipses.
(26.) Cycas pectinata (Cycadeae, Fam. 224).--A young leaf, 11 ½ inches in length, of which the leaflets had only recently become uncurled, was observed during 47 h. 30 m. The main petiole was secured to a stick at the base of the two terminal leaflets. To one of the latter, 3 3/4 inches in length, a filament was fixed; the leaflet was much bowed downward, but as the terminal part was upturned, the filament projected almost horizontally. The leaflet moved (see Fig. 114) largely and periodically, for it fell until about 7 P.M. and rose during the night, falling again next morning after 6.40 A.M. The descending lines are in a marked manner zigzag, and so probably would have been the ascending lines, if they had been traced throughout the night.
Fig. 114. Cycas pectinata: circumnutation of one of the terminal leaflets, traced from 8.30 A.M. June 22nd to 8 A.M. June 24th. Apex of leaflet 7 3/4 inches from the vertical glass, so tracing not greatly magnified, and here reduced to one-third of original scale; temp. 19o - 21o C.
CIRCUMNUTATION OF LEAVES: MONOCOTYLEDONS.
(27.) Canna Warscewiczii (Cannaceae, Fam. 2).--The movements of a young leaf, 8 inches in length and 3 ½ in breadth, produced by a vigorous young plant, were observed during 45 h. 50 m., as shown in Fig. 115. The pot was slided about an inch to the right on the morning of the 11th, as a single figure would have been too complicated; but the two figures are continuous in time. The movement is periodical, as the leaf descended from the early morning until about 5 P.M., and ascended during the rest of the evening and [page 253] part of the night. On the evening of the 11th it circumnutated on a small scale for some time about the same spot.
Fig. 115. Canna Warscewiczii: circumnutation of leaf, traced (A) from 11.30 A.M. June 10th to 6.40 A.M. 11th; and (B) from 6.40 A.M. 11th to 8.40 A.M. 12th. Apex of leaf 9 inches from the vertical glass.
(28.) Iris pseudo-acorus (Irideae, Fam. 10).--The movements of a young leaf, rising 13 inches above the water in which the plant grew, were traced as shown in the figure (Fig. 116), during 27 h. 30 m. It manifestly circumnutated, though only to a small extent. On the second morning, between 6.40 A.M. and 2 P.M. (at which latter hour the figure here given ends), the apex changed its course five times. During the next 8 h. 40 m. it zigzagged much, and descended as far as the lowest dot in the figure, making in its course two very small ellipses; but if these lines had been added to the diagram it would have been too complex.
Fig. 116. Iris pseudo-acorus: circumnutation of leaf, traced from 10.30 A.M. May 28th to 2 P.M. 29th. Tracing continued to 11 P.M., but not here copied. Apex of leaf 12 inches beneath the horizontal glass, so figure considerably magnified. Temp. 15o - 16o C. (29.) Crinum Capense (Amaryllideae, Fam. 11).--The leaves of this plant are remarkable for their great length and narrowness: one was measured and found to be 53 inches long and only 1.4 broad at the base. Whilst quite young they stand up almost vertically to the height of about a foot; afterwards [page 254] their tips begin to bend over, and subsequently hang vertically down, and thus continue to grow. A rather young leaf was selected, of which the dependent tapering point was as yet only 5 ½ inches in length, the upright basal part being 20 inches high, though this part would ultimately become shorter by being more bent over. A large bell-glass was placed over the plant, with a black dot on one side; and by bringing the dependent apex of the leaf into a line with this dot, the accompanying figure (Fig. 117) was traced on the other side of the bell, during 2 ½ days. During the first day (22nd) the tip travelled laterally far to the left, perhaps in consequence of the plant having been
Fig. 117. Crinum Capense: circumnutation of dependent tip of young leaf, traced on a bell-glass, from 10.30 P.M.