222 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
formed, not from the cells which have passed over into a resting con- 
dition, but either from the meristem of the growing point or from the 
cambium of these leptome wedges. 
C4) Structure of Organs. 
Female Catkins in Populus.* * * § — Mr. T. Meehan records an instance 
of a young tree of Populus tremuloides in which some of the catkins 
consisted entirely of female flowers, while in others about one-third of 
the scales bore stamens only, and about two-thirds pistils only. 
Opening of the Buds of Woody Plants.j — Mr. A. S. Hitchcock 
describes and delineates the mode in which a number of native American 
trees and shrubs unfold their leaves. 
Vernation in the Composite, Campanulaceae, and Lobeliaceae.f — 
Herr F. Eeinecke has examined the mode in which the leaves are folded 
up in the bud in a large number of species of Compositae belonging to 
different tribes, and finds no general characteristics in this respect for 
the different groups. In the Campanulaceae the mode of vernation is 
much more constant. 
Spiny Plants.§ — M. A. Lothelier discusses the morphological 
nature of the spines in various plants, classifying them under three 
heads, viz.— (1) branch-spines; (2) leaf-spines; (3) spurs ( aiguillons ), 
by which he understands a spine not containing any vascular bundle. 
There are also various intermediate conditions between the typical forms. 
The spines of Xanthoxylon and of Capparis spinosa are spurs ; those of 
Xanthium spinosum are peduncles concrescent with stipules ; those of the 
cupule of Castanea vulgaris , and of the fruit of Datura, 2Esculus 
Hippocastanum, Ricinus communis , and Caucalis daucoides, have the 
morphological value of leaf- teeth. The author finds the formation of 
spines to be largely dependent on the external conditions of the indi- 
vidual. The saturation of the air with moisture, and the diminution of 
light, have a tendency to reduce the differentiation of tissues, and con- 
sequently the production of spines. Under these conditions the number 
of stomates is also reduced. 
Comparative Anatomy of Leaves. || — According to M. C. de 
Candolle vascular bundles occur in the pith of the leaf-stalk and veins 
of a large number of Dicotyledons. In most Rosaceae the xylem- 
elements are wanting towards the upper side of the leaf. 
Leaves of Irideae.1T — Dr. H. Ross completes his account of the 
leaves of Irideae by the description of those belonging to a large 
number of different genera. The leaves are completely bifacial and 
dorsi ventral only in the genera Crocus and Syringodea , in the section 
Juno of Iris, and in Romulea crocifolia ; in all other cases examined the 
surface of the lamina corresponds morphologically to the under surface 
* Proc. Acad. Nat. Sci. Philadelphia, 1893, p. 289. 
f Trans. Acad. Sci. St. Louis, vi. (1893) pp. 133-41 (4 pis.). 
X ‘ Ueb. d. Knospenlage d. Laubblatter b. d. Compositen u s.w.,’ 63 pp. and 
1 pi., Breslau, 1893. See Bot. Centralbl., lvi. (1893) p. 100. 
§ Piev. Ge'n. dc Bot. (Bonnier), v. (1893) pp. 48^-3, 518-28 (8 pis.). 
|| Ber. Schweiz. Bot. Gesell., 1892, pp. 35-6. See Bot. Centralbl., lvi. (1893) 
p. 372. IT Malpighia, vii. (1893) pp. 315-90. Cf. this Journal, 1893, p. 500. 
