From George Henslow   [c. 20 February 1878]1

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 1st 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 1st Ed. p 497

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

An: des Sc. Nat. 5e 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.

diagram

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.)

AmemS

1
The date is established by the relationship between this letter and the letter to W. T. Thiselton-Dyer, 19 and 21 February [1878].
2
Van Tieghem’s paper on the cotyledon of grasses in Annales des sciences naturelles (botanique) (Tieghem 1872) was summarised in Bulletin de la Société botanique de France 20 (1873): Revue bibliographique, pp. 42–3.
3
Marcello Malpighi, Charles François Brisseau de Mirbel, Antoine Poiteau, Pierre Jean François Turpin. ‘Pileole’ is an obsolete term for the coleoptile (the hollow cylindrical sheath with a closed pointed tip that protects the shoot tip or plumule of grass seedlings). The term ‘lobule’ usually refers to a small portion or part of a lobe of a leaf; the usage here comes from Mirbel (Tieghem 1872, p. 241), for whom it is synonymous with the epiblast. The scutellum is a tissue within the embryo that absorbs the stored food from the endosperm; it was generally regarded as the cotyledon by the earliest writers but by the time Van Tieghem wrote his article, many botanists viewed the coleoptile (pileole) or the plumule as the cotyledon. The epiblast (lobule) is now thought to arise from the coleorhiza, but some botanists regarded it as a rudimentary second cotyledon. ‘Arrested 2nd Cotyledon of Dicots’ is grammatically misleading since Henslow means that the lobule (epiblast) is homologous with the second cotyledon of dicotyledons, not that the second cotyledon is arrested in dicotelydons. Tigellum is used here as an alternative term for the plumule or primary shoot.
7
Salix is the genus of willows; Populus is the genus of poplars. ‘Fibrovascular bundles’: a strand in the vascular system of stems and leaves of higher plants, consisting of xylem and phloem. See Tieghem 1872, p. 247.
8
Malpighi 1675–9 (reference is in fact to 1: 78, not 1: 77); Gaertner 1788–91; A. L. de Jussieu 1789; Brisseau-Mirbel 1815; Richard 1811; A. de Jussieu [1842] (the page reference seems to be incorrect); Lestiboudois 1848; Gris 1864; Duchartre 1867.
9
‘General presence of Albumen’ is a reference to what is now called the endosperm, the tissue surrounding the embryo in seeds of flowering plants; it provides nutrition. The term is from Gaertner 1788–91, 1: cxxxviii.

Please cite as “DCP-LETT-11219,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-11219