Ph Van Tieghem on Cotyledon of Grasses.

An: Sc. Nat. 5me. Ser. 14. 240. & 15. pp 236–273. abr. Rev. Bibl. Bull. de Soc. Bot. Fr. Jan–Mars. 1873. p 43.²

Opinions on the Nature of the Cotyledons of Grasses.

I. The ‘Shield” or Scutellum is the entire cotyledon. The “Lobule’” opposite to it is a second independent leaf (arrested 2nd Cotyledon of Dicots) The “Pileole”, is a 3rd leaf at 180° from the second (the Lobule). Finally, the first green leaf is the 4th of the entire Embryo.

(Malpighi, Mirbel, Poiteau, Turpin &c)³

II. The shield is still the Cotyledon, but the lobule is a dependance of it. The Pileole is the 2nd leaf of the embryo. The first green leaf is the 3rd.

(Schleiden, Schacht, Decaisne &c)⁴

III. The Pileole represents the entire cotyledon The shield and the lobule being only expansions of the Tigellum or of the Radicle. The first Green leaf is, then, the second appendage of the embryo.

(Richard, Adr. de Jussieu, Lestiboudois, Hoffmeister, Sachs &c)⁵

IV. The shield is the median part of the Cotyledon. The lobule is an opposite appendage of it. The Pileole is the ascending sheath (double axillary stipule) as in stipa. These three organs only compose one single cotyledonary leaf. The first green leaf constitutes the 2nd leaf of the plant.

(Gaertner,⁶ Mirbel (at first) Tigheim?)

Tigheim objects to the 1^st View; because the lobule has no vascular vessels. (But may it not represent an early stage of arrest before fibrovascular bundles are traced out at all? Cf. the glandular protuberance of Salix, regarded by some as an arrested axis, others as arrested perianth (of Populus):⁷ but it is so far as I have observed quite devoid of f.v. bundles G.H.)

Tigheim objects to II.— That the pileole would not be immediately in front of (i.e same side) as Shield.—

" objects to III. That the fibrovascular bundles would make an ear-like curve and return into the stem; whereas they ramify like a leaf.—

Authorities:—

Malpighi— Anatome Plantarum t. 1. p 77. fig 324–5

Gartner De fructibus et seminibus plantarum 1788. t.1. p. CXLIX.

A. L. de Jussieu Genera plantarum pp. 22 & 28

Mirbel. Éléments de physiologie Vegetale t.1. p. 65—pl 58 & expl.

L. Ch Richard. Analyse botanique des Embryos “Endorhizés”. Ann. du. Mus. 1813. t XVII. p 455 p. 473.  t. XIII. p. 424. note—

Jussieu Éléments de botanique 1^st Ed. p 497

Lestiboudois. Phyllotaxie Anatomique, Ann. des Sc Nat. 3^e Ser. 1848. t. x. p. 141.

An: des Sc. Nat. 5^e ser. 1864. t. II. p. 71.

Duchartre El. de Bot. 1867. p. 906. & 903.⁸

(I incline to first view and regard the lobule as the arrested opposite cotyledon and the pileole as the first leaf.

The Embryo of Monocotyledons appears to shew 3 points of “arrest”. (1) primary or axial root (2) one Cotyledon. (3) The general presence of Albumen.⁹

The numerous instances of truly distichous leaves (as in epiphytal orchids): or of tristicous (as in Carex) the prevailing forms in Monocots: results at once from the fundamental condition of the Cotyledon.— 2/5 &c results as usually in Dicots.—

G. H.)