12
fig. 18) that it lies as a thick pad in the sinus between the radicle and the smaller cotyledon,
indented in its turn by the vertical invagination to which the upper surface of the testa is
practically reduced. But such a section further shows that the peripheral pressure exerted
by the growing cotyledons has not, as in many campylotropous seeds, been sufficient to
obliterate completely the cushion of albumen on which they impinge ; a sheet of albumen,
much attenuated it is true but still readily discernible, separates the larger cotyledon from
the overlying testa. In a longitudinal section of the seed we further observe that the
plumule does not extend upwards beyond the middle, while the invagination of the testa
does not pass below that level. Consequently in a horizontal section below the middle we
find that the albumen has a figure-of-eight shape, the smaller loop embracing the radicle,
the larger enclosing the cotyledons with the plumule between them, while a single layer of
testa surrounds the whole (PLATE 2, fig. 20). In a horizontal section above the middle we
find, on the other hand, that the albumen is in two rings separated by the invaginated testa
which is now figure-of-eight shaped ; the cotyledons within the larger ring of albumen have
now no plumule between them (PLATE 2, fig. 21).
The presence of albumen was first pointed out by Bentham and Hooker.1 Most of
the early authors have, however, seen and figured it though, not knowing what it was, they
have not figured it very exactly and in many instances, with the actual tissue before them,
have followed Agardh 2 in denying its existence. The latest author of outstanding
authority to do this was Baillon 3 ; the only authors, prior to Bentham and Hooker, who
have attempted to explain the tissue, which no one can well fail to see, were Le Maout and
Decaisne,4 who supposed it to be an albuminoid thickening of the endopleura. While
Bentham and Hooker are the first to recognise its existence, the account they give of it is
not quite exact for they describe it as unilateral, and plentiful round the radicle. It is
plentiful round the radicle and it is most abundant on the upper side between the radicle
and the cotyledons, but it is not strictly unilateral ; it forms a complete covering to the
embryo. Their not quite accurate expression has, however, been adopted both by Engler 5
and by the writer6 ; this error should be avoided by future authors. An almost accurate
description of the conditions present was given by Harz7 who, however, recognises as the
remains of the body of the nucleus only 3 or 4 layers of small cells underneath the testa, and
describes the bulk of the albumen as endosperm. These layers of cells seen by Harz, who
has been followed in regard to the statement and the deduction from it, by Macchiati, 8 are
supposed by Briosi and Tognini to be possibly the tegmen of the seed. Judging from the
figures they may be tegmen, or they may be only the outer much compressed layers of the
albumen. Whether the tissue that Harz and Macchiati take to be perisperm is part of the
covering of the seed or part of the remains of the body of the ovule, there is no doubt that
these botanists err in describing the bulk of the albumen as endosperm. Had this been the
case the albumen would not necessarily have ended at the margin of the chalazal disk ; it
would probably not have persisted along the convexity of the larger cotyledon and it would
possibly have filled more completely the available testa round the radicle. In any case,
whether it ended at the margin of the chalaza or not, it would not have been organically
1 Genera Plantarum iii. p. 357.
2 Theoria Systematis Plantarum : Lund, 1858 ; p. 256.
3 Hist. des Plantes, vi, p. 215.
4 Traité de Botanique ; Paris, 1868 : p. 508.
5 Natürlichen Plansenfamilien, iii. 1. 97
6 Bengal Plants ; Calcutta, 1903 :
ii. 960.
7 Landwirthschaftliche Samenkunde, ii. p. 890.
8 Sulla sessualita, etc., della Canapa : Modena, 1889: p. 13.