92 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
difference in the degree of tension in elements separated from one another 
by a lignified membrane. 
(2) Other Cell- Contents (including: Secretions). 
Composition of the Sap.* — M. A. Hebert has investigated tho 
chemical composition of the sap in a species of Ampelocissus and in Musa 
paradisiaca. In the former he finds a comparatively large amount of 
iron, the sap becoming blue on long exposure, probably in consequence 
of the formation of iron- salts of gallic acid. In the sap of Musa potas- 
sium oleate was found, the source of its use for saponification. In the 
sap of the wood of black grapes, he found cenotannins, hitherto known 
only in the fruit. 
Localisation of Amygdalin "and Emnlsin in Eriobotrya. f — In 
Eriobotrya japonica M. L. Lutz finds the distribution of these two sub- 
stances to correspond with that in other genera of Pomese. Amygdalin 
is present in the very minute embryo (i.e. in the hypocotyl, plumule, 
and radicle), and in the cotyledons ; emulsin in the cotyledons only. 
Amygdalin was found in cells dispersed through the parenchyme of the 
cotyledons, and in the parenchymatous cells of the phloem of the vascular 
bundles. 
Production of Gum in the Sterculiacese.j — According to M. L. 
Mangin, the normal production of gum in this order of plants is limited 
to canals or lacunae buried in the parenchyme of the pith or of the 
cortex. Usually the gum does not escape outside the stem or branch, 
but there are some cases in which it does. The formation of this 
gum is effected by a special mechanism. The walls of the cells which 
border tho canals become gradually thickened and transformed into 
gum, while the outermost cell-wall retains its cellulose character with- 
out alteration. 
(3) Structure of Tissues. 
Central Cylinder of the Root.§ — Herr A. Kattein describes the spe- 
cial structure of the central cylinder of the root in a large number of 
Dicotyledons and Monocotyledons, and discusses the question whether 
it has the same value in the two classes of plants. This question he 
answers in the affirmative, and maintains that in these two classes, as 
well as in Conifers, it consists of separate xylem- and phloem-bundles, 
and of fundamental tissue. As in the embryo the two plerome-cones of 
the stem and of the root which face one another by their bases are alto- 
gether homologous, so also the whole inner portion of the stem (vascular 
bundle and fundamental tissue), and the central cylinder of the root, 
which both originate in the plerome-cones, have the same morphological 
value. In the stem each phloem-portion, with its xylem-portion, deve- 
lops into a closed vascular bundle, both portions lying on one radius. 
In the root this union does not take place ; the xylem and phloem-por- 
tions lio alternately side by side, each on its own radius. The funda- 
mental tissue of the root is homologous to that of the stem. 
* Bull. Soc. Chim. Paris, xiii. pp. 927-32; xvii.-xviii. pp. 88-91. See Bot. Cen- 
tralbl., 1897, Beih., p. 280. 
t Bull. Soc. Bot. France, xliv. (1897) pp. 263-5. Cf. this Journal, 1897, p. 303. 
{ X Comptes Rendus, exxv. (1897) pp. 725-8. 
§ Bot. Centralbl., lxxii. (1897) pp. 55-61, 91-7, 129-39 (2 pis.). 
