ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
639 
excelsa. It occurs specially frequently in the Cruciferse; the largest 
proportion being 2 ‘5 per cent, of the dried substance. In all cases 
where glutamin has at present been found, the seeds contain abundance 
of oil, though the seedlings from some oily seeds (poppy, Tropseolum , pine) 
contain asparagin and not glutamin. 
Structure of Starch-grains.* * * § — From the minute study of starch- 
grains obtained from a variety of different plants, Herr J. H. Salter 
comes to the following general conclusions. In all stages of its growth 
the starch-grain is sharply differentiated from the plastid in which it is 
formed ; its substance is excreted, and is not produced by gradual trans- 
formation of successive layers of protoplasm. Staining experiments 
show that the stratified appearance of starch-grains is the result essen- 
tially of variations in density, i. e. in the capacity for absorption of the 
different layers. All growing starch-grains appear to have a denser 
margin which is not stratified. The lamella attain their final differen- 
tiation only when they are covered by those formed later. A progressive, 
but not uniform, decrease in density may be detected, advancing from 
the margin to the nucleus of the grain. Observation of grains in process 
of solution renders it probable that changes may in some cases take 
place in the surface of the grain from the action of a ferment. The 
relation of the plastid to the starch-grain in process of solution appears 
in some cases to confirm Meyer’s view that the ferment is excreted by 
the chromatophore. As regards the inner structure of the starch-grain, 
all the phenomena lead to the conclusion that each lamella, or at least, 
each watery lamella, consists of a series of elements deposited radially. 
Arsenic in Plants.f — Herr J. Stoklasa reports the results of a care- 
ful series of observations on the presence of arsenic in the vegetable 
kingdom, and on its poisonous effects on plants. He states that arsenious 
and arsenic acids are both highly poisonous to plants, even in excessively 
minute quantities, and that arsenic acid is not able to replace phosphoric, 
as has been stated. Arsenic is, however, a very widely diffused element, 
especially in association with sulphuric acid ; in superphosphates it may 
even be present to the extent of 0*3 per cent.; but its presence in the 
form of As(OH) 3 or AsO(OH) 3 is not injurious to vegetation unless it 
exceeds 0 * 4 per cent. 
Ferment in Barley.J — MM. E. Bourquelot aud H. Herissey find, in 
germinating barley-seeds, in addition to amylase and trehalase, a soluble 
ferment which has a special action on pectin. 
Raphids in Monocotyledons.§ — Mr. J. Parkin describes the presence, 
in certain genera of Liliacem and Amaryllidem, of raphid-cells inter- 
mediate between those of ordinary structure in which a bundle lies in the 
centre of the cell surrounded by a mucilage-sheath, and those of Iris, in 
which each crystal-sac contains a large acicular crystal, and has a nucleus 
and protoplasm, but no mucilage. The raphids in question were ob- 
served in Funkia ovata, Convallaria majalis, Phormium tenax , Tritoma 
* Jalirb. f. wiss. Bot. (PfefFer u. Strasburger), xxxii. (1898) pp. 117-66 (2 pis.). 
t Zeitschr. f. d. landwirtsch. Yers. in Oesterreich, 1898, p. 154. See Bot. Cen 
tralbl., lxxv. (1898) p. 304. 
X Comptes Bendus,cxxvii. (1 898) pp. 191-4. Cf. this Journal, ante, p. 218. 
§ Ann. of Bot., xii. (1898) pp. 147-51 (1 ph). 
1898 2 X 
