60 NINTH REPORT. 



matter in solution is absorbed into the root hair which is simply an elongated 

 epidermal cell of the root, by the forces involved in the process of osmosis. 

 It is transferred from this cell to neighboring cells by a similar process, the 

 movement being generally from the cell containing the more dilute solution. 

 In all living cells this dilution is constantly changing by the action of the 

 protoplasm, consec[uently movements of liquids are set up. But the root 

 hairs are constantly a])sorbing from the soil and losing to the neighboring 

 cells, therefore a movement would be developed from the root hairs towards 

 the center of the root where the conducting tubes are situated. The soil 

 water is then carried from the soil to the vessels in the root by osmosis. It 

 is forced out of the cells adjoining the vessels by turgor pressure which pres- 

 sure is maintained merely by increase of cpiantity of material within the cell. 

 The peculiar arrangement between the cell and the vessel assists very ma- 

 terially. The releasing of water from the cell to the vessel is one of the most 

 difficult steps to explain. It is not easy to see how a cell can absorb water 

 on one side and give it out on the other, and this by the same process. A 

 reference to the ordinary osmometer made from pig's bladder, thistle tube 

 and molasses, may illustrate the point. The solution in the tube becomes 

 greater and greater until the tube overflows. It keeps on overflowing at the 

 top and this tube may be compared to the cell adjoining the vessel, the upper 

 end to the side of the cell touching the vessel, and the l:)ladder end to that 

 joining the neighboring cell. This assumes that the side of the cell next the 

 vessel is more pervious to water than the other side, and that the membrane 

 on the side next the other cell is different in some way from that on the side 

 next the vessel. The former assumption is supported by the fact that well 

 developed pits or openings between cell and vessel can readily be seen. The 

 latter is supported by the membrane theory of osmotic activity, which states 

 that the membrane itself, as well as the substance in solution, or the liquid 

 have to do with the attraction. 



The drop now being in the vessel of the root, all the other factors already 

 mentioned have more or less to do with the ascent through the vessels and 

 wood cells of the root, through the vessels and wood cells of the stem and 

 branches, and then into the vessels of the petiole, veins and veinlets of the 

 leaf. From these vessels it is taken up into the active green cells of the leaf 

 by osmotic action. After a time these cells become extremely turgid owing 

 to absorption and other vital activities in the cells, and there is a tendency 

 to relieve this tension by a release of some of the liquid through the sides of 

 the cell offering least resistance, and this is evidently on the side next the air 

 of the intercellular space. Consequently water oozes out into the inter- 

 cellular s])aces and is there taken up by the atmosphere, because when in 

 this intercellular space it is connected directly with the open air through the 

 stomates. But it should also be said that a portion of the water of the drop, 

 and practically of the matter in solution, is used in the green cells. Not 

 necessarily all of the water which is taken in at the root reaches the leaf be- 

 cause a considerable portion may be taken l^y the various tissues along the 

 way, to supply the losses resulting from drying out. With regard to the 

 root hair itself, a loss of substance to the surrounding soil often results. So 

 that the root hairs do not merely absorb. It is inevitable that they also 

 give out, from the very nature of the process involved in absorption; but this 

 giving out will depend upon the character of the soil water, mainly with re- 

 gard to its density, and to the substances in solution ; and also upon the con- 

 tent of the vacuole of the root hair. The plant overcomes this loss, to some 

 extent, by providing continually a new set of root hairs which contain about 



