ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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important deviations in structure from both Dicotyledons and Mono- 
cotyledons. 
The nucellus is at first naked, but is afterwards covered by two 
teguments. The suspensor is composed of two elongated cells, which 
subsequently divide by longitudinal walls. From the suspensor is 
formed a kind of caj) which developes into an aril covering the embryo 
on the whole of the side which faces the raphe. Between the nucellus 
and the embryo is a layer of absorbing cells which appear to serve as 
organs for the transmission of albuminoid materials from the nucellus to 
the embryo. 
The outer tegument of the seed is derived directly from the outer 
tegument of the ovule, and from the transformation of its parenchymatous 
and vascular elements. The mature embryo must be regarded as an 
amorphous maRs, a true thallome, on which is developed a single bud ; 
it is a degraded embryo with only a single cotyledon. This degradation 
of the embryo resembles that which occurs in parasitic and semi- 
parasitic plants, such as Orchideae, Orobanclie, Cynomorium , Balanophora, 
Monotropa, Cuscuteae, &c.,. and in some aquatic genera, e. g. Zostera, 
Hydrocharis, Utricularia, &e. In Trapa, as is always the case in 
Monocotyledons, the single cotyledon is not lateral, but terminal ; but 
the plumule does not make its appearance in a lateral niche of the coty- 
ledon as it developes, but in the slender portion from which the root is 
produced ; and the protecting scale (regarded by some authors as a 
second small cotyledon) appears behind the germinal tubercle. Except 
in the absence of endosperm, the development of the embryo resembles 
that in typical Monocotyledons. 
Comparative Anatomy of Leaves.* — According to M. C. de 
Candolle, intramedullary vascular bundles in the petiole and veins of 
the leaf are far more frequent among Dicotyledons than has hitherto 
been supposed. He has found them in members of 42 distinct families 
scattered through all the classes. He finds also that the Rosacese, with 
the exception of the tribe of Chrysobalanese and a few species in other 
tribes, are characterized by an imperfect internal structure shown by the 
absence of vascular bundles on the upper surface of the leaf. 
Leaves of Irideae.j — Prof. R. Ohodat describes the anatomical struc- 
ture of the leaves of the following genera of Irideas : — Iris, Crocus, Gladi- 
olus, Montbretia, Crocosma, and Sisyrinchium, and finds distinguishing 
characters in the details which are useful for purposes of classification. 
These depend mainly on the structure and arrangement of the vascular 
bundles, and on the structure of the cortical parenchyme. The stereids 
are less lignified in proportion as they are in direct contact with the 
fibrovascular bundles. 
Leaves of Eucalyptus.} — Sig. G. Briosi describes in detail the ana- 
tomical structure of the leaves of Eucalyptus globulus, which are of three 
kinds, — the cotyledonary, the younger horizontal, and the later sickle- 
shaped vertical leaves ; there is a gradual passage from the second to 
* Arch. Sci. Phys. et Nat., xxvi. (1891) p. 501. 
t Tom. cit., pp. 496-500. 
J ‘ Ric. int. all’ anatom, d. foglie d. Eucalyptus globulus,’ Milano, 1891, 95 pp. and 
20 pis. See Bot. Centralbl., xlix. (1892) p. 817. 
1892. 2 E 
