ZOOLOGY AND BOTANY, MICROSCOPY, ETO. 
213 
oosphere is somewhat larger than the nuclei of the synergids, and often 
contains three or four nucleoles of different sizes. 
The author then compares in detail the vegetative and the heterotype 
modes of cell-division. The structure of the resting nucleus is in both 
cases the same. The differences relate to the distribution of the chromo- 
somes, and to the connection between them and the spindle-fibres. 
Embryo of Gramineae and Cyperaceae.* — In the structure and de- 
velopment of the embryo in these two natural orders, M. P. Van Tieghem 
finds additional reasons for a wide separation between them in a natural 
system of classification. 
In the Gramineae, belonging to the Inseminatae, the fruit consists of 
embryo, endosperm, and a pericarp closely concrete with the latter ; there 
is no true seed. The embryo lies laterally and below in the endosperm, 
which completely surrounds it ; but at the point where the embryo 
comes very near the pericarp, the nutrient tissue forms only a very thin 
sheath. The embryo is straight, and consists of an endogenous radicle, 
and a plumule which bears the scutellum, usually an epiblast, the closed 
germinal sheath known as the coleoptile or pileole, an open green sheath 
on the other side of the scutellum, and the first green leaf above the 
pileole. The stem may lengthen between the scutellum and the germinal 
sheath, the plumule being then elevated on a stalk — the epicotyl or 
pedicle. Grasses with a sessile plumule are comparatively few — Triti- 
cum, Hordeum, Secale, &c. ; those with a stalked plumule are again 
divided into the Plagiodesmae and the Prenodesmae, dependent on the 
structure and course of the vascular bundle. 
The fruit of the Cyperaceae contains a true triangular seed, in the 
axis of which is the embryo, surrounded by a layer of endosperm, which 
is here very thick in the neighbourhood of the embryo. The embryo is 
straight or curved. It consists of an exogenous radicle, a plumule, a 
club-shaped foliar organ which remains enclosed in the seed, and a 
closed sheath, which often opens at a later period. The anatomy of the 
leaves and the structure and arrangement of the vascular bundles differ 
greatly from those in grasses. The sheath and the club-shaped leaf 
must be regarded as the two halves of one and the same organ, viz. the 
single cotyledon, and the bud enclosed in the germinal sheath is the 
plumule. 
Van Tieghem points out the very great separation from one another 
which these differences in structure indicate. The Cyperaceae must 
retain their place among the Monocotyledones ; while the Gramineae 
occupy a transitional position between the Monocotyledones and the 
Dicotyledones; and the author proposes to erect them into a new 
class, the Anisocotyledones. They were originally Dicotyledones, in 
which one of the two cotyledons has gradually aborted, but still remains 
in some cases in a rudimentary condition, the epiblast. This organ is 
never present in the Cyperaceae. 
Homology of the Embryo of Grasses.f — Herr L. Celakovsky dis- 
cusses the various theories that have been advanced respecting the 
homology of the different parts of the embryo of grasses, and sums up 
* Ann. Sci. Nat. Bot., iii. (1897) pp. 259-309. Cf. this Journal, 1897, p. 313. 
t Bot. Ztg., lv. (1897) l te Abt., pp. 141-74 (1 pi.). 
1898 
Q 
