82 SUMMARY OF CURRENT RESEARCHES RELATING TO 



slow growth, and produce roots of endogenous origin. In their function 

 of root-hearing organs they bear a resemblance to the rhizophores of 

 Selaginella. 



Nyctagineae.* — From the special examination of three species, Mira- 

 bilis Jalapa, M. longiflora, and Oxybaphus nyctagineus, Herr A. Heimerl 

 gives the following as the most characteristic peculiarities of the order : — 



The ovule presents an intermediate form between the campylotropous 

 and anatropous. The conducting apparatus for the pollen-tubes is re- 

 markably well developed. The three antipodal cells are already invested 

 with cell-walls before impregnation, and continue for a time after this. 

 The endosperm is inconsiderable in quantity, and transitory ; the peri- 

 sperm, on the other hand, very fully developed. The wall of the ripe 

 pericarp is of complicated structure, with a central sclerenchymatous 

 layer, and an outer layer containing tannin. Cells containing raphides 

 are very abundant in the short prolongation of the floral axis on which 

 the ovary is seated, and in the lower part of the pericarp ; in smaller 

 quantity also in the wall of the ovary ; they are altogether wanting in 

 the ovules. The ripe fruit is inclosed in a very thin brown skin, formed 

 by the fusion of two layers, the outer of which is developed from the 

 outer epidermis of the ovary, the inner and stronger one from the testa 

 of the seed. 



Root-tubers and Bacteria.! — Herr P. Sorauer sums up succinctly 

 the results of the observations of Tschirch, Woronin, Kny, Brunchorst, 

 Hellriegel, Eriksson, Frank, Benecke, and Moller, on the true nature of 

 the root-tubers in Legurninosse, as well as in Eleeagnaceas and in Alms. 



/3. Physiology . J 

 (1) Reproduction and Germination. 



Insect relations of Asclepiadese.§ — Mr. C. Robertson describes 

 the insect relations of certain Asclepiads. He states that while in 

 ordinary flowers an insect may be a useful visitor if it can reach the 

 nectar, in Asclepias many other conditions influence the insect relations. 

 Of visitors whose tongues are suited to the nectaries, many are useless, 

 because they do not light upon the flowers (Sphyngidte, iEgeriadse, and 

 Trochilus) ; others because their legs are not long enough to extract 

 pollinia (MegacMle). Others, again, rest their feet so lightly as seldom 

 to effect pollination ; e. g. Diptera and small butterflies ; while others 

 are not strong enough to free their claws from the slits and break the 

 retinacula. In all seventeen species were found to be killed on this 

 account. 



The author describes in detail several species of the genus Asclepias, 

 and also two species of Acerates. 



Fertilization of Flowers. || — Dr. J. MacLeod has added a sort of 

 appendix to the classic work of Hermann Miiller on the fertilization 

 of flowers. He has extended and corroborated the work of the great 



* Denksckr. K. Akad. Wiss. Wien, liii. (1887) 3 pis. 



t Bot. Centralbl., xxxi. (1887) pp. 308-14, 343-5. 



% This subdivision contains (lj Reproduction and Germination; (2) Nutrition 

 and Growth (including Movements of Fluids) ; (3) Irritability ; and (4) Chemical 

 Changes (including Respiration and Fermentation). 



§ Bot. Gazette, xii. (1887) pp. 207-16, 244-50. 



|| Arch, de Bio]., vii. (1887) pp. 131-GG (1 pi.). 



