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Show 306 MODIFIED CIRCUMNUTATION. CHAP. VI. beneath the horizon. The nocturnal position depends chiefly on the curvature of the petiole close to the blade, but the wh?le pe t1. 01 e becomes slightly curved downwadrd s. I· t deserves ·n odtic e tl t edlings of this and the last-name speCies were ra1sc at t~: :~a of February and another lot in_ t~c middle of ~iarcl_1, and the cotyledons in neither case oxhrlnted any nyctltrop1c movement. 1 ,.,a bona-nox.-The cotyledons after a few days grow to pom'-" d . b . s~ . 1 an onormo Us Sl. ze , those on a young .s ec lmg emg 4 mc 1es m· 1) rea dtl They were exten<lod honzontally at noon, and at 1. . F' d ft 10 t d at 63° beneath the honzon. rvc ays a or- P.M. S 00 . l t t d t ·wards they were 4& inches in breadth, _and at mg 1 ones oo a 64o and the other 48° beneath the honzon. Though _the bla~es . tb' t from their great size and from the petioles bemg aie m, yo · · 1 t · I t be long, we imagined that their doprcsswn at mg t m~g 1 . d et ormm· e d b Y tbe1'1· weight·' but when the pot was lmd h1o· n h-t 11 they became cuTved towards the hypocotyl, w uc. zon a y, t could not have been in tho least aided by their movemen h t · t d ·ds weight, at the same time they were somow at. WIS c upwar through apogeotropism. NovcrtheloRs, the wmght .of the cotyledons is so far influential, that when on anothc:· mght the p~t was turned upside down, they wc~·c. unable to nse and thus o assume their proper nocturnal posrtwn. , k }pom.a'a coccinen.-The coty1 c d ons w1 1 1' l's t young do no. t shm. at night but when grown a little older, b u t s t1'l l on ly ·4 bm e Ill lenbo-th (~neasured as before) and ·82 in brlca~th, tthlcyat· eicalOO~e greatly depressed. In one case t} te Y weor e wnzon a he' r at 47o' and at 10 P.M. one of them stood at .64 ~nd a!~ t~c petioles, beneath the horizon. The bla<les arc tlun, th t which become much curved down a t m·g h t' are shWorti ths oa ll thilo here weight can hardly have pro<luced any effcdct. tile same above speci.e s of Ipomrea, w h en tl 10 t ' vo cotyle ons. on d to seedling were unequally depresse d a t m·g h td dtl us,. seeme 0 . the day depend on the position which they had hol unno with reference to th~ light. , cot lcdons rise so Sola11Um lycoperstcum (Solane.ro).- rhe 'by so of s. palina· much at night as to come nearly m contact. 'I 0 1 d ,.sen only · d by 10 PM. 1a 11 cantla1m were hol'lzontal at noon, an ·. 1 · ht they 27° 30·' · but on the followm. g m01m·n g b 0 fo 1· e 1t was f1 tgl 1 e S!IJllO stood at' 59° above the horizon, an d m· t.h e a ftef rntlo onc ooty ledon· s of d~LY were again horizontal. The behavwur 0 10 this latter species seems, therefore, to be anomalous. CHAP. VI. SLEEP OF COTYLEDONS. 307 MirabiUs.f•tlapa and longijlora (Nyctaginero).-Thc cotyledons, which are of unequal size, stand horizontally during the middle of the day, and at night rise up vertically and come into close contact with one another. Rut this movement with M. longi;lora lasted for only the three :111-st nights. Beta vulgaris (Polygonero).-A large number of seedlings were observed on three occasions. DUl'ing the day the cotyledons sometimes stood sub-horizon tally, but more commonly at an angle of about 50° above tho horizon, and fo1· the first two or three nights they rose up vertically so as to be completely closed. During the succeeding one or two nights they ro. e only a little, and afterwards hardly at all. .Amarantl!us caudatus (Amaranthacero).-.At noon the cotyledons of many seedlings, which had just germinated, stood at about 45° above the horizon, and at 10.15 P.M. some were nearly and others quite closed. On the following morning they were again well expanded or open. . Ounnabis sativt(, (Cannabiucro ). -We arc very doubtful whether this plant ought to be here included. The cotyledons of a large number of seedlings, after being well illuminated during the da!, were curved downwards at night, so that the tips of some pomted directly to the gr·ound, but tho basal part did not appear to ~ at all depressed. On the following morning they were ~gaiU flat and horizontal. The cotyledons of many other seedII~ gs were at the same time not in any way affected. Therefore tins case seems very different from that of ordinary sleep, and ~robably comes. under the bead of epinasty, as is the case with 1e.Ieave~ of this plant according to Kraus. The cotyledons aro heliotropic, and so is the hypocotyl in a still stronger degree. all~alis:-We now come to cotyledons provided with a pulvinus, fwhich are remarkable from the continuance of the nocturnal r:ements during several days or· even weeks, and apparently a dr growth has ceased. 'l'he cotyledons of 0. r·osea jloribwHlc~ an urt' z t · 1 ' wu a a sm { vertically down at night and clasp the upper r:rt of the hypocotyl. Those of 0. Valdiviana and Strlsitiua on . toe contrary, rise vertically up so that their upper SUl'faces c~me In close t t· ' are claspedc obny athc , atu dl adf ter the yo. ung leaves. are developed thes.e zontall e co Y c. ons. As m the daytime they stand hon-lll . Y, or are even a little deflected beneath the horizon they ~m~ . ' com r e evenmg through an angle of at least 90°. Theil' P Icated circumnutating movements durjng the day have X 2 ,:,: |