^ 



268 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Vasa propria of Phalaris nodosa.* — G. A. Pasquale finds the 

 subterranean buds of this grass from Sicily, 1-2 cm. long, to be 

 enclosed in a fourfold sheath, destitute of chlorophyll, but filled with 

 a bright red sap. The peculiar vessels filled with red sap are found 

 also in the leaves, their number varying between sixteen and twenty- 

 four, according to the breadth of the leaf. These vessels extend quite 

 straight from the base to the apex of the leaf, and with no interrup- 

 tion to their cavity, except two or three oblique septa when the leaf is 

 young. That they are not to be confounded with intercellular 

 passages is shown by the indei^endence of their walls, so that they 

 can readily be isolated from the rest of the tissue. 



The red fluid in the interior of these vessels is mucilaginous, 

 slightly granular, thickens and coagulates in the air. The author is 

 uncertain whether it is properly a pigment or latex. It is regarded 

 by the Sicilians as poisonous. 



Explosive Stamens.f— The sudden bursting of the anthers in the 

 families Urticacefe and Morese, by which the pollen is suddenly thrown 

 out, has long been known. E. Askenasy has examined the structure of 

 the organ concerned in Parietaria erecta, Urtica dioica, and Pilea serpylli- 

 folia. In these species he finds the outer side of the filament covered 

 with strong transverse ridges lying close to one another. The explosion 

 has been supposed to depend on the sudden straightening of the pre- 

 viously strongly curved filament, from the removal of the pressure of 

 the petals. But, according to Askenasy, this is not the case, at least 

 in Parietaria erecta, where the cause is the development of the com- 

 pressed, elastic, turgescent tissue of the filament itself. 



Arrangement of Molecules in Trajectorial Curves caused by 

 Growth.,^ — Professor Schwendener discusses the growth of organized 

 structures by intussusception in reference to the consequent necessary 

 twofold arrangement of the molecules, viz. in layers parallel to the 

 surface, and in rows at right angles, or nearly so, to that direction. 

 On the surface, for example, of a young starch-grain, every small 

 portion, as it grows to a greater distance from the organic centre, 

 must take a definite course, the direction of which is shown by the 

 fissures which residt from drying up or from unequal swelling. From 

 a mechanical point of view, all the forces which influence growth may 

 be regarded as decomposed into two groups, a radial and a tangential. 

 If the radial force alone were supposed to be in action in a mass of 

 concentric layers, and the growth equally vigorous in the direction of 

 all the radii, straight rows of molecules would be formed at right 

 angles to the layers. But when the energy of growth has attained a 

 maximum in the direction of any given radius, and then decreases on 

 both sides, the radial rows pass into orthogonal trajectors, i. e. into 

 lines which, traversing a system of curves, cut each of them at 

 right angles. 



* Eendiconti R. Accad. Sc. Fis. e Matem. Naples, xix. (1880) p. 144. See 

 Bot. Centralbl., ii. (1881) p. 76. 



t Verhandl. naturw.-med. Ver. Heidelberg, ii. pp. 274-82 (1 pi.). See Bot. 

 Centralbl, i. (1880) p. 1366. 



X MB. k. Akad. Wiss. Berlin, 1880, pp. 408-32 (1 pi.). 



