i6 PLANT PHYSIOLOGY 



to show that the amount of water raised in the unit of time is enough to com- 

 pensate for that lost in transpiration ; all that has been done has been to 

 prove that water can be raised to the required height by the assumed forces. 



1. 39, for 139 read 103-8 ; for two read one and a half 



1. 41, for 20 m. read 15 m. 



1. 42 P. 64, 1. i6,for Let us take . . . supplied to the leaves read In other 

 cases, and frequently even in high trees (e.g. Coniferae, Morus, Fraxinus, 

 Acer pseudoplatanus ; compare WIELER, 1893), a bleeding-pressure of only 

 12, 21, 313 mm. has been found ; further, it must be specially noted that the 

 maximum pressure occurs only in spring, before the leaves come out. Later 

 on, when transpiration is active, the pressure within the tree is generally less 

 than that of atmospheric air, i.e. there is a so-called negative pressure (see 

 pp. 53 and 71). 



64, 11. 52-4, for It is obvious ... of air entirely, read HULETT (1903) replaced 

 the gypsum by a porous porcelain plate in which a precipitate of copper- 

 ferrocyanide had been laid down. In this way the permeability of the plate 

 to air was greatly decreased, and accordingly, with a barometric pressure of 

 74-4 cm., HULETT obtained a mercury column in the tube in-i cm. in height. 



65, 11. 5-6, for it would . . . produced by read one would produce obviously 

 a vacuum when the mercury reached a height corresponding to the 



I. 23, after (1900) read and HULETT (1903) 



66, 11. 1-4, for If in place . . . conditions obtaining read It is of interest, in 

 respect of the conditions obtaining in the plant, to note that STEINBRINCK (1906) 

 with the aid of his high-tension siphon has proved that a considerable cohesion 

 can also be shown to exist in a rapidly flowing liquid. Further, a certain 

 percentage of dissolved air does not at once destroy the cohesion (DixoN and 

 JOLY, 1894), but doubtless that percentage must not be excessive, for it was 

 noticed quite generally that a rupture of the stretched water column is the 

 more readily prevented the more the air is extracted from it. If now, in place 

 of the porcelain plate used in HULETT'S experiment, we employ a clay cell, in 

 whose wall a precipitation membrane has been laid down, the apparatus would 

 present a great likeness to the conditions obtaining 



II. 20-37, /or At the same moment . . . cells of the root, read The osmotic 

 pressure in leaf parenchyma is, however, very high. EWART (1905) often 

 found it to be equivalent to a 6 per cent., 8 per cent., or even 10 per cent, solution 

 of KN0 3 . In the last case a force = 46-7 atmospheres or 482 m. of water would 

 have to be overcome before plasmolysis could take place. Again, since EWART 

 has shown (1905, p. 78) that leaves on the lofty branches of a tree have a dis- 

 tinctly higher osmotic pressure than those inserted lower down, it is of the 

 utmost importance that detailed researches should be made as to the amount 

 of this pressure. Certainly one must not measure the suctional power of the 

 water column pendent to the cell by its length only ; we must take into account 

 as well the friction against the walls of the vessels and the opposition to its 

 passage presented by the living root-cells. 



67, 11. 2-i6,for The following table . . . 10-66 cm. read Typical tracheids (Pinus) 

 have a diameter of 0-03 mm. and a length of as much as 4 mm. Those of 

 Nelumbium (0-6 mm. broad and 120 mm. long) remind one of vessels, which 

 latter may often be narrower than tracheids, but, at the same time, may be 

 2-3 m. in length. We may readily convince ourselves of the great length of 

 tracheae by blowing through a dry stem of Cobaea, whose lower end has been 

 submerged. 



68, 11. 2-7, for In the spiral . . . the three types read The thin regions are 

 spoken of as ' pits ' ; these pits are, in annular and spiral tracheae and tracheids, 



