814 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
tli g fruit of several Borragineae. In the cystolith it occupies the whole 
of the original organic framework, and exhibits, after the removal of the 
lime, a fine stratification, and the characteristic ornaments or sculpturing. 
In the hairs and epidermal cells it occurs in different forms, and often 
in regions where there is no calcium carbonate. 
Comparative Anatomy of Parasites.* — In the two volumes published 
of this work M. A. Chatin treats of the following orders of parasitical 
flowering plants : — Balanophoreae, Cassythaceae, Cuscuteae, Cytineae, 
Epirhizantheae, Loranthaceae, Monotropeae, Orobancheae, Kafflesiaceae, 
Bliinantheae, and Tliesieae, including 70 genera. 
In the Cassythaceae the epiderm possesses numerous stomates, except 
on the absorbing organs. Tracheids are absent from the stem, but occur 
in the flowers and in the embryo. The vessels lose their tubular form, 
and become short and elliptical in their passage from the stem to the 
absorbing organs. Air-cells occur in the xylem-system, with the excep- 
tion of the parenchyme. The stomates are placed at right angles to 
the epidermal cells. Phloem is wanting ; there are no medullary rays. 
Among the Monotropeae Hypopitys multiflora presents several pecu- 
liarities, especially in the absence of absorbing warts, except in one 
instance. 
Corky Excrescences on the Stem of “ Zanthoxylum.”| — Mr. C. A. 
Barber describes the nature and development of the corky excrescences 
on the stem of several species of “ Zanthoxylum ,” and appends a list of 
plants whose thorns have a basal cork-formation. The structure of the 
corky cushion at the base of the thorn differs in its details in different 
plants. It is probable that, in the majority of cases, the function of the 
cushion is the retention of the thorn, at any rate in the young plant, 
after secondary thickening has commenced. In Rosa, however, its 
purpose appears to be the prevention of a rupture of the tissues on the 
forcible separation of the thorns. In Cactus the tough cushion at the 
base of each bunch of spines serves to glue together the spines and 
prevent their becoming detached. 
Histology of Lauracese.j; — An essential oil is found in all species 
of this order examined by M. E. Perrot; it is contained either in 
special cells or in vesicles scattered through the parenchyme; and 
the bark always contains a great number of large mucilage-cells. 
The greater number of the oil-glands are usually located in the bast. 
In some genera, as Cinnamomum and Laurus , the mucilage-cells are 
mostly seated in the bast ; in Sassafras in the pith. All the various 
kinds of cell may in some cases be detected in the embryo. 
Structure of Aquilariese.§ — M. P. Van Tieghem records the occur- 
rence, in the Aquilarieae, a tribe of the Thymelaceae, of phloem-islands 
in the secondary xylem. By this character the structure of the wood of 
the Aquilarieae is sharply distinguished from that of the Thymeleae, the 
other tribe of its order. 
* ‘ Anat. Comp, des vegetaux ; plantes parasites,’ Paris, 1892, xv. and 560 pp. and 
113 pis. See Bot. Centralbl., li. (1892) p. 211. 
t Ann. of Bot., vi. (1892) pp. 155-66 (1 pi.). 
+ ‘Contrib. a l’etude histol. d. Laurace'es,’ Paris, 1891, 62 pp. See Bot. Centralbl., 
1892, Beih., p. 274. 
§ Journ. de Bot. (Morot), vi. (1892) pp. 217-9. 
