Chaparral

Movement of water.-The ascent of water in vessels containing chains of water and air bubbles (Jamin's chain) may take place ill one of two ways: either the whole chain moves upward or the water alone moves while the air bubbles are stationary. SCHAPOSCHUIKOFF'4 claims that the physical conditions of a Jamin's chain in the conducting vessels of plants are not such that they prevent the movement of the chain as a whole. Reasoning theoretically, he concludes that the presence of cross walls in the vessels do not hinder such a movement. The bubble just above the cross wall and the one just below are under unequal pressures, the former under reduced pressure owing to the suction from above, and the latter under increased pressure owing to the rise of water below. On account of the increased pressure the bubble below goes into solution, passes through the cross wall, and separates out again under the reduced pressure above. It is assumed that the bubbles arise only from gases dissolved ill the water filling the vessel. They separate out when the water consumption by the plant is greater than the supply, causing a reduced pressure in the vessels. The author constructed a very ingenious apparatus to put the above theoretical conclusions to the test of experimental proof. In his apparatus gas bubbles began to form from the gases in solution when the pressure reached one-half to one-third of an atmosphere in a glass tube corresponding to a conducting vessel in the plant. As soon as a gas bubble reached the cross wall, the filtration of water through the membrane ceased. The manometer soon showed an increased pressure in the tube, due to the continued rise of water from below. After a short time the bubble went into solution and passed through the water-saturated membrane, allowing the filtration of water to continue. The manometer now showed a sinking of pressure again. The passage of the bubbles by the sculpturing of the wall may be explained in a way similar to their passage through the cross walls. As soon as a bubble is held by a thickening in the wall, unequal pressures are set up, causing it to dissolve sufficiently to pass on.-CHAS. 0. APPLEMAN.