444 
SUMMAHY OF CURRENT RESEARCHES RELATING TO 
but carbohydrates. But an investigation of the mucilaginous matter 
found in the tuberous roots of the yam, Dioscorea japonica and D. batatas , 
showed that it contains nitrogen, and possesses all the essential charac- 
teristics of animal mucin. 
Mucilage of the Malvaceae.* — M. A. Guiraud lias investigated the 
distribution of the mucilages in the officinal Malvaceae, especially in 
Malva sylvestris and Althsea officinalis. He states that the receptacles 
are not of lysigenous origin, as has usually been stated. The mucilage 
is found in all the organs, and results from the gelatinisation of the 
walls of special cells found only in the secondary parenchyme. It may 
remain in enclosed cells, or may flow out into passages or receptacles 
formed by a dissociation of the tissue. 
In the root the formation of the mucilage coincides with that of the 
secondary structures. In the stem of Malva the mucilage-cells appear 
first in the pith, then in the cortical parenchyme, the collenchyme, and 
the hypodermal parenchyme ; it is most abundant in the periphery of 
the stem, where it arises partly in the cells, partly in the intercellular 
spaces. In the leaf its formation follows a similar course to that in the 
stem, occurring both in the cells and in special receptacles ; it is espe- 
cially abundant in the leaf of M. sylvestris. Mucilage is very abundant 
in the flowers of Althsea and Malva, but its distribution is very variable ; 
in M. sylvestris it occurs in large quantities in the epiderm of the calyx 
and epicalyx, and in the fundamental parenchyme of the petals. 
Presence of Emulsin in Manihot.f — M. L. Guignard notes the 
presence of emulsin in several Brazilian species of Manihot which 
yield the starch known as manioc. Its localisation is the same as that 
of papayin in the Papayacese, viz. in the laticiferous system of the 
embryo. Myrosin is also present, but not within the laticiferals. 
(3) Structure of Tissues. 
Cuticnlarisation and Cutin.f — M. C. Van Wisselingh has established, 
by physical and microchemical investigations, an essential difference 
between the processes of cutinisation and suberisation. Cork is never 
formed at an early period ; it always makes its appearance in the 
phellogen on the inner side of the cell-wall, and is in direct contact 
with the protoplasm. The cuticle, on the other hand, is always present 
in the embryo, clothing the outer side of the epidermal cells; it is 
always separated from the cell-contents by layers of cellulose. 
Cutin always consists partially of fusible constituents, though the 
temperature at which their fusion takes place varies greatly, from below 
100° to 200° C. Phellonic acid is never present. Cutin is, as a rule, 
less easily saponified by potassium hydrate than suberin. The products 
of saponification differ from the corresponding products in the case of 
* ‘ Du developpement et de la localisation des mucilages chez les Malvacees 
officinales,* Toulouse, 1894, 117 pp. and 4 pis. See Bot. Centralbl., lxi. (1895) 
p. 376. 
f Bull. Soc. Bot. France, xli. (1894) Sess. Extraord., pp. ciii.-vii. Cf. this 
Journal, 1894, p. 468. 
X ‘ Over Cuticularisatie en Cutine,’ Amsterdam, 1894, 32 pp. and 2 pis. See Bot. 
Centralbl., lxii. (1895) p. 234. 
