ITO 



SCIENCE. 



[Vol. II., No. 27! 



BOTANT. 



Influence of diminished atmospheric pressure 

 on the growth of plants. — Experiments conducted 

 by Wieler at Tiibingen show, that, all other external 

 conditions being the same, plants will grow more rap- 

 idly under diminished atmospheric pressure. Thus, 

 if a specimen of the common Windsor bean (Vicia 

 faba) be grown in a receptacle in which the pressure 

 of the air can be controlled, it will be foimd to grow 

 faster until the pressure has been diminished to 100- 

 300 mm.; the normal pressure under which the an- 

 cestors of the plant have flourished being, of course, 

 not far from 700 mm. If, however, the pressui-e is 

 reduced below the smaller figure given above, the 

 rate of growth diminiihes. Wieler found that the 

 curve of growth of the sunflower is about the same 

 as that of the bean. It was further shown by his 

 experiments, that growth is retarded by increased 

 pressure until the minimum is reached at 2-2| atmos- 

 pheres, from which point there is again an increase. 

 Although the short abstract of these interesting re- 

 sults so far published is meagre in the extreme, it in- 

 dicates that the field entered upon by Wieler (and by 

 Bert in France) may compel us to revise some notions 

 now held in regard to the adaptation of plants to their 

 surroundings in past ages, and at the present time 

 upon high mountains. — (liotaii. zelL, July 6.) a. l. g. 



[188 



Pollination of Cypella. — Two Brazilian species 

 of this genus of Irideae have been studied from time 

 to time by Fritz Miiller, who finds a number of inter- 

 esting peculiariiies in their flowering. The flowers, 

 like those of Cordia, etc., ai'e produced in abundance 

 only on certain days, which recur more or less regu- 

 larly, and apparently independently of climatic con- 

 ditions. Nectar is secreted in pockets on the tliree 

 petals, which are flexible, so that when a Xyloeopa 

 or Bom bus, to whicli the flowers seem well adapted, 

 alights on one in quest of nectar, it bends over with 

 the weiglit of the bee, whose back is brought in 

 contact with a stigma and tlie underlying anther. 

 Commonly the bee goes immediately to another 

 flower without trying the other petals of the one on 

 ■which it has first settled, so that crossing is eHected 

 by it. One of the species studied proves to have 

 self-impotent pollen: the other is fertile with its own 

 pollen. The stingless bees (Trigona), though not 

 necessarily excluded by structural peculiarities from 

 the nectar, do not obtain it readily; yet their visits 

 for the protectively colored (pale-bluish) pollen are 

 sufficiently numerous to prevent the larger bees from 

 visiting the flowers in numbers. — {Berichte dmUch. 

 6o«. (/e,seZisc/(., Aprils, 1883.) w. T. [189 



ZOOLOGY. 



_ {Gejieral 2}liy&iology and embryology.) 

 Influence of gravity on cell-division. — E. Pflii- 

 ger, by placing fresh laid frogs' eggs in a watch-glass, 

 and adding a little water with semen, and pouring it 

 off in a few seconds, was able to impregnate the eggs 

 without allowing the gelatinous envelopes time to 

 swell. The eggs then adhered to the glass, and so 

 could be brought iiito various positions. The first 



division occurs in three hours, and always in a verti- 

 cal plane, no matter how the axis of the egg lies. 

 When the axis of the egg (from dark to white pole) 

 lies horizontally, the plane of division is still always 

 vertical, but may form any angle with the ovic axis. 

 The influence of gravity is also shown in that the 

 upper pole divides more rapidly than the lower. If 

 the position of the egg is exactly reversed, this still 

 holds true, and development progresses; so that 

 repeatedly the medullary furrow, with its high boW 

 dering ridges (nervous system), was found upon the 

 xohite side when this was uppermost. Out of seven- 

 teen eggs, twelve developed so that the median plane 

 of the body of the embryo coincided with that of the 

 first division of the yolk. (This fact of a relation 

 between the lines of cleavage and the axes of body is 

 not novel, as Pfliiger seems to think: there are many 

 observations on various animals which prove such a 

 relation.) From these experiments it results that 

 the topography of the organs is not determined by 

 the arrangement of the substance aroimd tlie axes 

 of the egg, but that the axis around which the organs 

 are grouped is determined by gravity. — (PJtiii/er's 

 arch. 2)lii/isiol., xxxi. 3U.) c. 8. M. [190 



Germ-layers of rodents. — A. Fraser finds in 

 the common gray rat and the house mouse the same 

 arrangement of the layers as in the guinea-pig. The 

 decidua appears to differ in the mode of its forma- 

 tion from that which ordinarily obtains; and the very 

 early, rapid, and voluminous formation of its solid 

 mass appears to have some close and constant rela- 

 tion to the peculiar inversion of the blastodermic 

 layers which is found in these rodents. — (Joitm. 

 roy. micr. soc. Lond., June, 1SS3, 345.) c. s. M. [191 



Intestinal absorption of fat by lymph-cells. 

 — Zawarykin has studied the small intestine during 

 active digestion, making sections stained with per- 

 osmic acid and picrocannine. The material was 

 obtained from dogs, rabbits, and white rats. The 

 lymph-cells are found between the epithelial cells 

 covering the follicle and in llie underlying adenoid 

 tissue, and finally in tlie mouths of tlie chylous 

 vessels. These cells alone contain any fat, being 

 charged with globules of various sizes. Their multi- 

 farious inegular forms, and the inconstant shape of 

 the nucleus, indicate that they were performing 

 active amoeboid movements when fixed by the osmic 

 acid. From these appearances Zawarykin concludes 

 that the lymph-cells (leucocytes) resorb the fat: they 

 enter the epithelium, seize the particles of fat by 

 amoeboid movements, then descend between the cyl- 

 inder-cells, through the sub-epithelial endothelium 

 and adenoid tissue, into the roots of the chylous 

 vessels. In Peyer's patches the cells are present in 

 crowds, and the resorption of fat seems par'icularly 

 active at those points. (The presence of lymph-cells 

 between the epithelial cells of the intestines has been 

 known for some time, but the significance of their 

 occurrence has not been heretofore understood. Sew- 

 all advanced the view that the immigrant cells remain 

 and become epithelial cells; but that appeared highly 



