ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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occur in the underground parts only, to the entire exclusion of the aerial 
organs. They were found in the largest quantities in S. erucsefolius and 
paludosus, to a smaller extent in S. Jacobsea, Cineraria , viscosus , and 
sylvaticus. The tissues in which they chiefly occur are the pith, the 
liber, and the cortical parenchyme. Other species gave negative results. 
Cholesterins of Cryptogams.* — M. E. Gerard has extracted the 
cholesterins from a number of the lower Cryptogams — Saccharomyces , 
Mucor mucedo , Lobaria pulmonaria — and finds that, like those of the 
higher plants, they belong exclusively to the class of ergosterins, differ- 
ing, therefore, from those of animals. M. Gerard gives the following 
test for distinguishing between animal and vegetable cholesterins. If 
the former are treated with concentrated sulphuric acid, a yellow colour 
is produced, and a white precipitate on diluting with water ; while the 
latter are coloured red by sulphuric acid, and yield a green precipitate 
on the addition of water. 
(3) Structure of Tissues. 
Oblito-Schizogenous Secretion-Receptacles of the Myrtacese. f — * 
From observations made on about twenty species of Myrtaceas, Dr. G. 
Lutz gives the following general account of these structures. The form 
of the receptacle is never that of a canal, but is usually globular or 
ellipsoidal. They are generally formed, at an early period, from one 
or two epidermal cells, distinguished from the rest by their granular 
contents. The original cell or cells divide, and the receptacle is formed 
schizogenously by the separation of the daughter-cells. The so-called 
resinogenous layer is formed on the walls of the secreting cells, in the 
form either of caps or of a continuous coating. It consists of a mucila- 
ginous ground-substance in which granules and rods are imbedded. The 
secreting cells become obliterated at an early period ; hence the term 
given to these structures by Tschirch of oblito-schizogenous secretion- 
receptacles. At a later period the walls of the receptacle become 
suberised. The secretion is formed in the resinogenous layer, which 
disappears as the secretion accumulates. When the receptacle is fully 
formed, the intercellular spaces become filled with the secretion, and the 
resinogenous layer disappears altogether or nearly so. The receptacles 
vary in diameter between 20 and 230 p. 
Porosity of Woody Sterns.^ — M. H. Devaux has conducted a series 
of experiments which demonstrate the great variation in the degree of 
porosity of the trunk of different trees. They may be divided into four 
classes : — (1) Those in which the stem has both a system of vessels and 
a system of cortico-medullary canals which often communicate with 
those of the leaves ; (2) Stems with a distinctly porous cortex and a less 
porous wood ; (3) Stems with a porosity which is essentially vascular, 
the cortex and pith being less porous and sometimes not at all, as in the 
vine ; (4) Woody stems only very slightly porous in their cortical 
region, i. e. from canals, and very little or not at all porous from vessels. 
* Comptes Rendus, exxi. (1895) pp. 723-6. 
t Bot. Centralbl., Ixiv. (1895) pp. 145-53, 193-202, 257-64, 289-301 (2 pis). 
X Mem. Sci. Phys. et Nat. Bordeaux, v. (1895) pp. 365-96 (3 figs.). 
