ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
295 
Structure of the Ovule as a Factor in Classification.* * * § — Pursuing 
his investigations on the variations in the structure of the ovule in 
Phanerogams, M. P. van Tieghem classifies the orders of Seminatae in 
two groups, the Crassinucellat^: and the Tenuinucellat®, according 
as the nucellus, on the one hand, remains considerable in bulk, up to the 
period of the formation of the embryo, or, on the other hand, is reduced 
to a single layer of cells, or entirely consumed by the endosperm. Each 
of these groups can be again divided into Unitegminatae and Bitegmi- 
natae. Of these four subgroups, by far the largest are the Crassinu- 
cellatae Bitegminatae, and the Tenuinucellatae Unitegminatae. The 
distribution among these four sub-groups of a number of natural orders 
is discussed in detail, the position of not a few being greatly modified 
when classified in accordance with the structure of the ovule. 
Embryo and Seedling of the Cactacese.l — Dr. W. F. Ganong de- 
scribes in detail the structure and development of the embryo and 
seedling and the mode of germination, in nearly all the 18 genera 
of Cactaceae. A distinctive feature of the germination is the rapid swell- 
ing of the hypocotyl, and the consequent immediate assumption of a 
succulent habit. When germination is completed and the epicotyl is 
about to appear, we find an immense range of form, from the very un- 
cactus like Pereskia to the nearly globular Mamillaria almost destitute 
of cotyledons. In general, the ground-form of the embryo answers to 
the ground-form of the adult, and alters with the latter by the working 
back of newly acquired characters. “ There is an occasional expansion 
of surface, with increased cotyledons and relatively diminished hypo- 
cotyl, allowed by exposure to more mesophytic habitat.” 
Dimorphism in Crucifer®. £ — Prof. R. Tate identifies the Australian 
Geococcus pusillus F. v. Muell., with Blennodia cardaminoides Benth. 
It differs, however, remarkably from the typical form. The flowers are 
very small and cleistogamous ; the plant is stemless, and the siliquas 
are very short, rather thick and turgid, and during ripening, bury 
themselves in the ground. 
Interruptions of the Axile Symmetry in Pedicels.§— M. Pitard lias 
studied the variation which takes place in the structure of the pedicels 
in compound inflorescences ( Heracleum , Sambucus ) dependent on their 
angle of inclination. The symmetry in the arrangement of the vascular 
bundles and in the outline of the pedicel may be modified by both in- 
ternal and external causes ; the orthotropous floral axis frequently pre- 
senting a bilateral structure. 
Bud- Variation. || — Herr L. Beissner enumerates the various kinds of 
bud-variation which occur especially in woody plants, resulting in the 
following forms : — pyramidal and columnar forms ; pendent and weeping 
forms ; dwarf forms ; forms with deeply divided or coloured leaves, &c. 
He points out the danger of confounding true bud- variations with varia- 
tions resulting from unfavourable or other peculiar vital conditions ; and 
* Journ. de Bot. (Morot), xii. (1898) pp. 197-220. Cf. this Journal, 1897, p. 313. 
t Ann. of Bot., xii. (1898) pp. 423-74 (1 pi.). Cf. this Journal, 1895, p. 546. 
X Trans. R.S. South Australia, xxii. (1898) pp. 122-4. 
§ P.-V. Seances Soc. Sci. Phys. et Nat. Bordeaux, 1898, pp. 34-43. 
|| S.B. Niederrhein. Ges. Nat. u. Heilk. Bonn, 1898, pp. 30-42. 
