ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
81 
layers than in the softer ones. The phenomenon of swelling is due to 
the trichites absorbing water and themselves swelling ; in other words, 
the water dissolves in the crystals. There are, however, two kinds of 
swelling — “ pore-swelling,” where water is merely imbibed between the 
crystals ; and “ solution swelling,” where it is taken up by the crystals ; 
it is the latter which initiates the disorganisation of the starch-grain. 
Starch-grains may grow in chromoplasts as well as in chloro- and 
leucoplarts ; they are always surrounded by a layer of plastid within 
the cytoplasm. They grow by apposition, the theory of intussusception 
being entirely discarded. Protoplasm is regarded as an emulsion, the 
elements of cell-walls and of starch-grains being crystallised out of it. 
The author proposes a new nomenclature and classification of the 
various kinds of starch-grain. In an anomalous form which colours 
reddish-brown with iodine, there is an unusually large proportion of 
amylodextrin. This form of starch is characteristic of a large number 
of saprophytes, but occurs also in many green plants. 
Starches.* — Mr. W. Griffiths gives descriptions, accompanied by 
photomicrographs, of the principal starches used as food, the greater 
number being from the Marantacere and the Gramineae. A short account 
is given with the illustration of the origin of the starch, each being 
magnified by 160 diameters. The mounting medium recommended is 
1 part glycerin with 7 parts camphor water or carbolic acid water. 
Localisation of Anagyrine and Cytisine.')' — M. P. Guerin has studied 
the occurrence of these alkaloids respectively in Anagyris fcetida and in 
several species of Cytisus , especially G. Laburnum. In both cases he 
finds them located chiefly in the epidermal cells and in the outer cortical 
layers ; they are present in the largest quantity in the cortex of the 
root and in the seed. In the seed, the alkaloid is located in the epiderm 
and parenchyme of the cotyledons, not in the integument. In G. Laburnum 
cytisine occurs also in the petals. Similar results were obtained in 
Baptist a and Thermoptis , two genera allied to Anagyris. 
Formation of Gum in Acacia. — M. L. Lutz has studied the pro- 
cess of gummosis in several species of Acacia. It commences in the 
cambium, the cell-walls of which display an acid in place of their pre- 
vious alkaline reaction, and thence spreads in both directions, outwardly 
and inwardly. When the medullary rays have been completely impreg- 
nated with gum, certain spots near the pith'exhibit a swelling of the cell- 
wall, and this marks the first exudation of gum ; it flows out into the 
cell-cavities of the fibres and of the xylem-vessels. From these it 
spreads to the parenchyme, which becomes transformed into a gummy 
mass. The processes are similar in other gum-producing genera. The 
reaction used for gum was the red colour produced with cassella red 
(0 • 25 parts neutral cassella red ; 20 parts 90 per cent, alcohol ; 30 parts 
distilled water). 
Silicon and Aluminium in Plants.§ — According to M. Camusat, 
aluminium is taken up by plants in the form of potassium or sodium 
* ‘The Principal Starches used as Food,’ Cirencester, 1802, 62 pp. and 21 photo- 
micrographs. f Bull. Soc. Bot. France, xlii. (1895) pp. 428-32. 
t Tom. cit., pp. 467-71. 
§ Bull. Soc. d’Hist. Nat. Autun, 1S95. See Bull. Soc. Bot. France, xlii. (1895) 
llev. Bibl., p. 535. 
1896 
G 
