10 
of Zostera as an outgrowth from the axis, and not as a leaf.” In this 
he agrees with Adr. de Jussieu. A. Gris, studying the embryo of Zea 
from a physiological standpoint, also regarded the cotyledon as a lat- 
eral expansion of the axis, modified in such a manner as to become the 
principal absorbing organ of the embryo. 
Duchartre? stated that the embryo is remarkable in having an oval, 
flat, or slightly curved, bud-like expansion at its base, called by Gaertner 
the “scutellum.” This organ directly adjoins the endosperm by its 
dorsal face. In front of it is another shoot, which Richard calls the 
*blaste? Le Maout and Decaisne? regarded the scutellum as a 
cotyledon, whieh is often split along its outer face, showing the rad- 
iele and plumule. The plumule is conical and composed of one to four: 
primary eonvolute leaves. They regarded the plumule sheath as the 
first leaf of the plumule. Sandeen* investigated a large number of 
ripe embryos and concluded that the scutellum is a thallus formation 
and that the plumule is a protuberance of the axis. 
Sachs? regarded the seutellum as an outgrowth of the axis beneath 
the cotyledon and the plumule-sheath as the cotyledon, enveloping the 
whole plumule like a mantle. Hanstein® studied the development of 
Brachypodium from the embryo sae to its maturity. He regarded the 
scutellum as a leaf and a cotyledon, and both the plumule-sheath and 
the epiblast as trichomatic projections. This is difficult to imagine. 
Van Tieghem’ reviewed the subject, illustrating the parts of the 
embryos of Triticum wstivum, Hordeum vulgare, Avena sativa, Phalaris 
canariensis, Zea mays, and Andropogon sorghum vulgare, briefly stating 
his own objections to the views previously held. He considered that 
the scutellum and plumule-sheath together represent the cotyledon, 
which has at its opposite side a small protuberance called the lobule or 
epiblast. Owing to the presence of two vascular bundles in the 
plumule-sheath, he calls it a double stipule united at the margins, and 
homologizes the scutellum and plumule sheath with the leaf and ligule. 
Hegelmaier? discussed the grass embryo from its developmental 
history, giving excellent figures of Triticum «stivum. He also noted 
the oceurrence of secondary roots in Coix, Hordeum, Secale, Avena, 
Triticum, and other genera, concluding with Van Tieghem that the 
‘Recherches anatomiques et physioloques sur la germination. Ann. des Sci. natu- 
relles, ser. 5, 2: 1864. 
* Eléments de Botanique. 1867 
? Recherches anatomiques et physioloques sur la germination. Ann, des Sci natu- 
relles, ser. 5, 2: 1864. 
Bidrag till kaenn ed omen om Grasembryots byggnad och Utweckling. Acta 
Univers, Lundens, 1868 
"Lehrbuchder Botanik, 474. 1868. Eng. Trans. and revision by S. H. Vines, 1882. 
*Die Entwickelung des Keimes der Monocot. and Dicot. Botanis. Abhand, 47. 
1870. Taf. 14, figs. 11-21; Taf. 15-18. ie 
ms les Cotyledons des Graminées. Ann. des Sci. naturelles, series 5, 15: 723-726: 
Zur Entwickelungsgeschichte 1 tylischer Keime, ete. Bot. Zeit. 1874. 
