[63]

Cucurbita ovifera Heel

(The Cucurb. must require to expose their Cots. as soon as possible to Light so as to assimilate.)

Dec. 15th 8° 30' a.m.

2 seeds laid flat, with radicle perpendicularly bent down .35 inch in length from tip of seed-coats have heel on lower side only a just perceptible transverse prominence about 1/10 of inch within apex of coats. In Tips of coats removed above & below marked with 2 tall pins.—

Dec. 16' 8° 30'. a.m. In the above 2 seeds heel now largely developed— Development wonderfully sudden— i.e in 24 hr.

Now examined 28 seeds laid flat on peat & covered by peat & in every one heel developed on lower side. In every one, except one case, the heel (which is flat on lower side & sloping on upper side) had caught tip of seed coats & arched hypocotyl was bursting open the seed-coats. I have seldom seen anything more pretty. [sketches]

I feel almost certain that seed must lie on one flat & natural side on ground for heel to act; for if f seed placed vertically as at B. hypocotyl & radicle will protrude in same line & apex or ridge of heel, (instead of flat lower side) will come into contact with tips of seed-coats & scrape over them, instead of splitting the coats open.

Begin by saying if seed not planted in natural position, but vertically apparatus will not act— showing coordinated adaptation.

Dec. 17th 8° a.m.— 9 seeds were buried with flat side vertical & longer axis horizontal [sketch] & in all these cases heel formed on lower side transversely to flat side of seed (∴ add 9 to above 18 seeds showing action of geotropism) Of the 9 4/9 freed themselves from their seed coats & 5/9 retained seed-coats after rising above Peat.— The heel would have rubbed slightly against both edge of orifice of Coats, instead of flat lower side side resting on lower lip of orifice.

(over)

[63v]

17th 9° a.m continued) 3 seeds placed with perpendicularly with radicle end downwards & both all 3 have risen with seeds coats on. 1 seed placed with radicle end upwards & this came up with seed coats on.

19th 1 with end of seed coats removed & has come up with seed-coats on.

1 with do do…with seed-coats shed.—

19th 15 laid flat, all have come up naked, except 2 doubtful as yet for still partially buried— peat excessively loose so very unfavorable for forming seed-coats. —

(21st Altogether 18 seeds were laid flat on natural position on peat & covered with layer & 17 of these came up above the friable peat with skins cast off.)

(Dec. 21 soaked in Permanganate 25 more radicles — Heel somewhat variable in form & size— grow at generally stained on edge, as well as beneath — occasionally narrow zone on upper surface — (say nothing about 2 knobs) I have seen secondary radicles developed from lower surface & 1 such radicle from upper surface

29 [+] 13 [=] 41

Flahault says heel belongs wholly to hypocotyl, but tested by permanganate of potash, which colour radicle, but not hypocotyl brown the lower flat surface of heel p is a part of the radicle & upper sloping side part of Hypocotyl— 8 seedlings were thus tested in 1 of the cases half if the whole heel was tinted brown, so that in this case more than the lower surface of heel belonged to radicle.—