ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
753 
nilk. The juice appears to contain three distinct proteids, two sepa- 
rable from the acid juice by heat alone, one at about 75° C., the other 
at 100°, while the third is not coagulable by heat, but is precipitated by 
acetic acid and potassium ferrocyanide. The proteid-digesting power 
of the juice is manifested in acid, neutral, or alkaline fluids, the ferment 
in this respect resembling trypsin rather than pepsin ; it acts most 
strongly in a neutral solution. A number of experiments are described 
on the influence of the reaction of the fluid, on the influence of tempera- 
ture, and on the rate of action. The proteolytic ferment may be 
separated from pine-apple juice either by saturation of the neutralized 
fluid with sodium chloride, or by saturation with magnesium sulphate, 
the former being the preferable method. It appears to be a mixture of 
a globulin and a proteose. 
Formation of Oil or Resin in Schizogenous Receptacles.* * * § — Herr A. 
Tschirch brings forward fresh evidence in favour of the view that in 
these receptacles the secretion is not formed inside the so-called “ secret- 
ing cells,” but from the gelatinized wall of these cells which faces the 
receptacle. 
(3) Structure of Tissues. 
First Formation of Vessels in the Leaves of Compositae.f — M. A. 
Trecul states that in those species of Composite which have narrow 
leaves, such as Tragopogon and Scorzonera , the first veins formed at the 
base of the leaf are always parallel to the mid-rib ; when they have 
extended to the whole length of the leaf they begin to anastomose with 
one another and with the mid-rib. A vascular network then makes its 
appearance a little below the extremity of the bundles at the summit of 
the leaf or still lower down; and this network then extends towards 
the base of the leaf. 
Tannin-cells in the Fruit of the Carob.J — Prof. R. F. Solla has 
followed out the development of the tanniferous cells which occur 
exclusively in the parenchyme of the fruit of Ceratonia siliqua. He finds 
them already in the very earliest stage of the young ovary. Their 
contents consist of a mixture of substances belonging to the group of 
tannins, with other substances of a proteinaceous character, the chemical 
reactions of which are given in detail. 
Structure of Prionium serratum.§— Prof. F. Buchenau publishes a 
detailed account of the structure of this conspicuous plant of the Cape 
flora, the only shrubby member of the natural order Juncaceae. It 
occupies an isolated position in the order, presenting some analogies 
with the fossil Restiaceae. One of its distinguishing characters is the 
abundance of scattered vascular bundles in the interior of the stem. 
Histology of Rheum. || — Herr J. C. Koningsberger describes the 
presence of peculiar resin-receptacles in the root and rhizome of BJieum 
* Ber. Deutsch. Bot. Gesell., xi. (1893) pp. 201-3. 
f Comptes Rendus, cxvi (1893) pp. 850-6. 
X Bull. Soc. Bot. Ital., 1893, pp. 121-4 ; and Malpighia, vji. (1893) pp. 209-42 
(1 pi.). 
§ Biblioth. Bot. (Luerssen and Haenlein) Heft 27, 1893, 26 pp. (2 pis. and 1 ) 
|] Bot. Ztg., li. l te Abtheil. (1893) pp. 85-8 (1 pi). 5 
