502 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Ovule and Seed of Rafflesia and Brugmansia.* — Graf zu Solms 
Laubach has studied the development of the ovule and seed in these 
two genera. The ovules arise on the walls of the fissures of the ovary 
in the ordinary way as conical projections, but before the complete 
differentiation of the epiderm. The apex of the curved ovular cone 
becomes the nucellus ; the embryo-sac originates from the terminal 
cell of its central row. As in the Orchidese, the ovules are not fully 
developed at the time of opening of the flower ; it is only later that 
the germinal vesicles and antipodals make their appearance ; probably 
only after pollination. The endosperm originates in the ordinary way ; 
not, as in many other parasites, by division of the embryo-sac. The 
embryo finally absorbs the endosperm, with the exception of its outer- 
most layer, which remains firmly attached to the seed till maturity. 
Hygroscopic Mechanism of Anthers and Hairs.f — Herr C. Stein- 
brinck now attributes the bending of the outer tangential walls of anther- 
cells to the pressure of water rather than to the shrinking of the radial 
wall ; the inner tangential walls offering a greater resistance to this 
pressure. In the peristome of mosses, the movement is rather due to 
a shrinking of the cell-wall. A similar phenomenon is observable in 
hygroscopic hairs, such as those of the seeds of Salix and Populus , 
those on the style of Clematis and Pulsatilla , the primary rays of the 
pappus of Composite, the awns of Pelargonium and Erodium, and the 
hairs on the seed-vessel of Geranium sanguineum. 
Mucilage of the Seeds of Cistacese.f — Herr 0. Rosenberg arranges 
the species of Cistaceae in seven groups dependent on the origin of the 
mucilage in the testa which varies greatly. It may result from the 
gelification of the outer side of the cuticle, or from that of the inner 
layers of the wall ; in Fumana from the gelification of all the walls of 
the epidermal cells. In the section Euhelianthemum there is an- internal 
as well as an external mucilage. In the testa of the seeds of most Cis- 
tacem starch is found, which the author regards as a product of excretion. 
It appears to take no part in the metastasis which accompanies germi- 
nation. 
Convolute Cotyledons.§ — Herr F. Hegelmaier has followed out the 
development of convolute cotyledons, especially in the Geraniaceae and 
Onagraceae. It does not appear to depend on any obvious mechanical 
cause. The embryo is neither strictly incumbent nor strictly accumbent, 
though approaching more nearly to the latter position. The convolute 
folding of the cotyledons is evident from the time that they are still 
small — not more than 0*3 mm. broad — their margins being at a con- 
siderable distance from the testa, and the endosperm has no influence on 
their development. Both the cotyledons develop unequally on the two 
sides, sometimes the right, sometimes the left side, but always the same 
for the two cotyledons. 
* Ann. Jard. Bot. Buitenzorg, 1898, 2 m0 Suppl., pp. 11-21 (1 pi.). 
t ‘Ueb. d. hygroskopischen Mechanismus v. Staubbeuteln u. Pflanzenhaaren,’ 
1899 (1 pi.). See Bot. Centralbl., lxxviii. (1899) p. 343. 
X Bih. k. Svensk. Vetensk.-Akad. Handl. Stockholm, xxiv. (1898) Afd. 3, 60 pp. 
(2 pis. and 5 figs.). § Ber. Deutsoh. Bot. Gesell., xvii. (1899) pp. 121-39 (1 pi.). 
