ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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so as to restore them to somewhat their original size, is the excess of 
the inner pressure in the water without, over that in the water within the 
cells. 
Mucilage as a Gliding-mechanism.* * * § — Dr. F. W. T. Hunger points 
out that mucilage, in addition to its protective function in the vegetable 
kingdom, has another purpose, analogous to that in animals, to allow 
newly formed organs to glide over one another without injury in rapid 
growth, or to promote the power of motility in parts of plants or in 
entire organisms. The following illustrations, among others, are 
given: — The mucilaginous envelope of the Oscillatoriace©, of diatoms 
and desmids, and of the hormogones in the Cyauophyce©; the large 
development of mucilage in the Florideae ; the invariable development 
of mucilage in the growing point and round the sexual organs of the 
Hepatic© ; the mucilaginous coating of root-tips and root-hairs ; the 
secretion of mucilage in the leaf-sheaths of the Polygonace© and of 
many other plants. 
Conducting Tissue of Vanilla Fruit.f — Herr A. Tschirch has made 
a careful study of the so-called “ tela conductrix ” of the fruit of the 
vanilla, and decides that it is a true conducting tissue, through which 
the pollen-tubes penetrate. Not only the outer but also the lateral walls 
of the epidermal cells which face the ovary, are converted into mucilage, 
the pollen-tubes passing through the gelified cell-walls. 
(4) Structure of Organs. 
Colours of Flowers, if — From an examination of a number of mono- 
cotyledonous flowers of North America, Mr. J. H. Lovell comes to the 
conclusion that the primitive colour of the perianth of monocotyledonous 
flowers was green. Yellow, white, and lurid or greenish-purple flowers 
have in many instances been derived directly from the primitive green ; 
red flowers have passed through a yellow or white stage; blue and 
purple-blue have been derived from yellow, white, or red forms. In 
general, among monocotyledons, yellow flowers are visited by flies and 
bees ; white flowers by bees, nocturnal Lepidoptera, flies, and beetles ; 
lurid-purple by flesh-flies ; red by bees and butterflies ; blue flowers 
chiefly by bees. Red and blue flowers usually have the honey concealed, 
which is a far more effective cause of the limitation of insect visits 
than colour. 
Periodicity in the Flowering of Dendrobium crumenatum. § — 
M. F. A. F. C. Went describes the phenomena connected with the 
opening of the flower of this epiphytic Orchid of Java. Not only all 
the flowers of an inflorescence, but all the flowers on the different 
plants in the same district, are open, as a rule, on the same day, wither- 
ing in the evening, whether growing in the sun or the shade. He 
regards this periodicity as due to internal causes, but modified and 
defined by external conditions. 
* Biol. Centralbl., xix. (1899) pp. 385-95. 
f Schweiz. Wochenschr. f. Chemie u. Pharm., 1898, No. 12. See Bot. Centralbl., 
lxxviii. (1899) pp. 105-8 (3 figs.). J Amer. Nat., xxxiii. (1899) pp. 493-504. 
§ Ann. Jard. Bot. Buitenzorg, 1898, 2 me Suppl., pp. 73-7. 
