ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
749 
stricta the leaf, composed of three leaflets, is horizontal during the day, 
but at the commencement of night each of the leaflets turns on its point 
of insertion. These movements, however, can be brought about in 
O. strida and various other plants, by three different causes: — (1) by 
darkness ; (2) by strong sunlight ; (3) by contact with a foreign body. 
Nocturnal sleep manifests itself by the same movements as diurnal 
sleep, but is due to a different cause, viz. to an augmentation of the 
quantity of water in the pulvinus at the base of the leaflet. In the 
evening, when transpiration ceases, water accumulates at this point. 
(4) Chemical Changes (including Respiration and Fermentation). 
Action of Diastase on Starch.* — From an extended series of obser- 
vations on a great variety of starch-grains — seeds of cereals, scales of 
the hyacinth and other bulbs, Leguminosae, &c. — Herr G. Krabbe 
is able to disprove finally the theory that the grains consist of two 
different substances, granulose and farinose. He shows also that diastase 
does not penetrate between the micellae of the starch-grain, but that 
the destruction of this substance by the diastase takes place in very 
much the same way as the solution of a crystal by the surrrounding 
medium. 
During germination (in the endosperm of wheat) a number of canals 
are formed on each side of the discharged starch-grain. These canals 
gradually extend to the interior of the grain, and have a somewhat 
spiral appearance (really annular) owing to the varying intensity of 
the action of the ferment on the different layers of starch, which vary in 
density. The sharply defined walls of these canals show that they 
cannot have been formed by an intermicellar action of the diastase on 
the substance of the starch, but that the molecules of starch are 
dissolved as such in these regions in centripetal succession. The 
transformation of starch into sugar is a secondary process not connected 
directly with the solution of the grain. The canals finally branch and 
anastomose, and cause the eventual complete breaking-up of the grain ; 
these fragments then finally disappear by solution. 
In large excentric starch-grains (potato, Lilium candidum, Orobanche , 
Lathrsea, &c.) the dissolution of the grain takes place in a somewhat 
different way ; it is effected very slowly and nearly uniformly, centri- 
petally, but may be accompanied by local formation of pits or crevices. 
The smaller grains of the potato are, however, destroyed centrifugally 
by the formation of canals, and frequently of a hollow in the 
interior. 
The author finds diastase present in the living cells of almost all 
parts of plants. The dissolution of the starch-grains does not appear to 
be brought about by microbes or other protoplasmic structures, since these 
cannot be detected in the canals by the Microscope or by microchemical 
reagents, and diastase is not immediately killed, as protoplasm is, by 
alcohol, but retains for a long time, when immersed in it, its fermentative 
power. Experimental observations on the action of bacteria on starch 
lead also to the same result. 
The cause of the inability of diastase to penetrate between the 
* Jahrb. f. Wiss. Bot. (Pringsheim), xxi. (1890) pp. 520-608 (3 pis.). 
1890. 3 G 
