88 SUMMARY OF CURRENT RESEA.IICHES RELATING TO 



of this tissue serves for the nutrition of the embryo-sac, and is ultimately 

 resorbed ; the outer portion takes part in the formation of the testa. In 

 the permanent tissue there is developed a much-branched system of 

 vascular bundles, and as these develope the rumination of the endosperm 

 makes its appearance. The testa of the ripe seed has a very complicated 

 structure. 



In other Anonaceae with ruminated endosperm the ovule has two 

 integuments, and the appendages spring from the inner of these ; they 

 have a very regular arrangement. The primary nucellus is ultimately 

 resorbed entirely. The first endosperm-cells are formed in the embryo- 

 sac, not by free-cell-formation, but by ordinary cell-division. 



Integument of the Seed of Geraniacese.* — Dr. G. B. de Toni de- 

 scribes the peculiarities of the Italian species of Geranium as respects 

 the seminal integument. He finds that they can be classed under three 

 heads, viz. : — (1) Seeds with areoles not exceeding 12 ya in diameter; 

 (2) seeds with areoles from 20 to 35 [x in diameter, nearly or quite regular, 

 having therefore a finely reticulated appearance ; and (3) seeds with 

 large areoles, at least 40 /a in one direction, hence reticulated, or with 

 minute pits. The genus belongs to the class characterized by having 

 hard seeds, with one or two protective strata of cells, and nearly or quite 

 destitute of endosperm. 



Hygroscopic Movements in the Cone-scales of Abietinese-t — Mr. 

 A. N. Prentiss calls attention to the fact that in most of the Abietinese, 

 soon after the ripening of the cones, the persistent scales fold backward 

 or outward from the axis to permit the ripe seeds to escape. The scales 

 are very sensitive to moisture, and in many species exhibit very rapid 

 movements when wet. Tliis is strikingly the case with Tsuga canadensis. 

 This property is very efficient, first, in loosening the winged seeds from 

 the scale which bears them, and, secondly, in securing their wide dis- 

 persion in different directions by the wind. 



Relationship of the Twisting Action of the Vascular Bundles to 

 Phyllotaxis.| — Dr. P. Teitz confirms Schwendener's view § as to the 

 mechanical origin of the special mode of phyllotaxis in any particular 

 species. It is the result of the action, during the formation of the 

 leaves, of the concurrence of definite forces of pressure and traction, 

 resulting in a regular law as to the arrangement of the leaves. 



Development of Floating-Leaves.||— Herr G. Karsten has investi- 

 gated the cause of the phenomenon that when aquatic or amphibious 

 plants whose leaves ordinarily float on the surface of the water grow 

 entirely in the air, their petioles elongate greatly. The observations 

 were mostly made on Hydrocliaris morsus-ranse, Itanunculus sceleratus, 

 and Marsilea quadrifoUa. The conclusion arrived at was that it is the 

 oxygen of the atmosphere which causes the arrest of growth of the 

 petiole of floating-leaves as soon as the lamina reaches the surface. 

 The same is the case also with the water-lilies ; while, on the other 

 hand, in Trapa natans and the batrachian Ranunculi, belonging to the 

 section B,. aquatilis, the elevation of the floating-leaves to the surface 



* ' Ricerche sul istologia del tegumento seminale del Geranii Italiani,' Venezia, 

 1888, 43 pp. (5 pis.). t Bot. Gazette, xiii. (1888) pp. 236-7. 



I Flora, Ixxi. (1888) pp. 419-39 (1 pi.). § See this Jom-nal, 1887, p. 475. 



II Bot. Ztg., xlvi. (1888) pp. 565-78, 581-9. 



