THE Microscope. 21 
Mecuanics or Roor-Apsorprion.*—De Vries has lately studied 
the young absorbing roots of plants, with reference to the mechanics 
of the tissues. He concludes from the following experiments that 
either the so-called ‘“‘ bundle-sheath ” (Kernscheide) or the pericamb- 
ium, or both, bear the root-pressure. A root of Iris Pseudacorus, 
12 em. long, with the root tips uninjured, was placed under a pres- 
sure of 35 em. of mercury. Every fifteen minutes a microscopically 
thin tangential section was cut from the root at a place 2 cm. from 
the tip. No water appeared at the surface of the cut until the 
sheath was reached, when immediately a drop was exuded. Similar 
experiments with like results were made upon the roots of Dipsacus 
Sylvestris, and the stems of various plants. He also shows how the 
sheath is adapted to resist the filtration of the water under root- 
pressure before it becomes suberized. De Vries also states that the 
movement of protoplasm in the cells which take up or transport 
water is such as to facilitate its passage to the vascular system in 
the interior. In the root-hairs the rotation is from one end to the 
other; in the epidermis parenchyma sheath and pericambium the 
chief stream passes over the tangential and transverse walls. The 
movement is strongest in the cells in which the absorption of water 
is greatest. As the suberization of the walls proceeds it gradually 
decreases, and ceases when the process is complete. 
HisronocicaL CHANGES FOLLOWING LigaTuRE oF A VESSEL. t—Bottger, 
following the work of Baumgarten, has investigated the histological 
changes induced by the ligaturing of a vessel. He proves that a 
proliferation of the endothelium of the intima takes place by means 
of karyokinesis, and that the growing endothelium is often separated 
from the wound, and remains in the still fluid blood-mass. In 
regard to the condition of the blood in the ligated vessels the author 
found that he could corroborate the statement of Baumgarten, that 
in aseptic operations the blood does not coagulate in the vessels. 
The red corpuscles may be found intact even after four weeks’ separ- 
ation from the circulation. The leucocytes undergo a fatty degener- 
ation by the seventh day or earlier—as the result of which the nucleus 
is concealed, but is still capable of being stained. The blood 
placques may remain intact after many days of blood stagnation. 
Finally, the author notes that in the stagnant blood there is a large 
number of single nucleated leucocytes in proportion to those having 
*Bot. Centralblatt, Bd. xxxv—76-1888. Bot. Gazette, September, 1888. 
+Centralblatt, F. Klin. Med. No, 26, 1888. 
