SUMMARY OF CURRENT RESEARCHES RELATING TO 
644 
occurs frequently in extrafloral nectaries, where there are great accumu- 
lations of formative materials. Its frequent presence in the stigmas of 
entomophilous plants, such as the haze], probably promotes the forma- 
tion and growth of the pollen-tubes. It is always entirely wanting in 
the guard-cells of stomates, where a low temperature is favourable, in 
order to promote the turgor of the cells and the consequent opening of 
the stomates. 
Physiology of Germination in Maize.* — In the light of a fresh 
series of observations on the chemical changes which take place during 
the germination of Zea Mays , Herr F. Linz reviews the researches of 
previous observers, and comes, on some points, to different conclusions, 
especially from those of Brown and Morris, in the case of barley.']' Since 
a fresh formation of diastase takes place in the isolated endosperm, 
he regards this as necessarily a living tissue. In the dormant condition, 
the living scutellum contains about nine times as much diastase as the 
endosperm. The quantity of diastase in all the organs increases with 
the energy of the transport of starch. Diastase is unquestionably pro- 
duced independently in the embryo. The epithele of the scutellum 
does not excrete diastase ; it appears to be an apparatus for absorbing 
nutrient material. 
Chemical Processes of Germination.^ — Herr D. Prianischnikoff 
confirms the conclusion of Boussingault that no regeneration of asparagin 
takes place in the dark in germinating seedlings. This substance is 
probably a product of the oxidation of albumin, like urea in the animal 
kingdom. 
Formation of Gum. § —According to M. L. Mangin, in the tissues of 
the vine in which the formation of gum takes place, the walls between 
the vessels and the adjacent parenchymatous cells are distinguished by 
the membranes of the pores consisting entirely of pectinaceous sub- 
stances. It is here that the formation of gum begins ; it becomes 
gradually more soluble in water, and is forced into the vessels, where it 
collects into large drops and forms a continuous layer on the inside of 
the vessel. A similar phenomenon takes place in other trees, as the 
chestnut, lime, elm, maple, AilanthuB , &c. 
y. General. 
Evolution of the Vegetative Phase of the Sporophyte.|| — Prof. 
G. F. Atkinson discusses the probable influence of disturbed nutrition 
on the vegetative phase of the sporopliyte. Spore-production in plants 
which themselves assimilate carbon dioxide is necessarily preceded by a 
greater or less development of chlorophyll-bearing organs. Within the 
life-cycle, therefore, chlorophyll-bearing organs or tissues are necessarily 
primary, while sporogenous organs or tissues are secondary. Injury to, 
or removal of, chlorophyllous organs forces the assimilation of carbon 
dioxide into other organs or parts, often dormant. In Angiosperms the 
* Jahrb. f. wiss. Bot. (Pfeffer u. Strasburger), xxix. (1896) pp. 267-319. 
f Of- this Journal, 1890, p. 633. 
X Landwirtli. Versuchs-Stat., xlvi. (1896) pp. 459-70. See Journ. Chem. Soe., 
1896, Abstr., p. 380. 
§ Rev. d. Viticulture, 1895, 16 pp. See Bot. Centralbl., lxvi. (1896) p. 389. 
Cf. this Journal, ante , p. 81. || Amer. Natural., xxx. (1896) pp. 319-57. 
