AGRICULTURAL BOTANY. 959 



In summarizing his results the author -states that the tl<>\v of water through 

 open vessels filled with sap takes place in accordance with Poiseuille's formula for 

 the flow through rigid tubes, any divergences 1 n >t i « •♦ •< 1 being due to tin- presence of 

 irregular internal thickenings in the vessels. The length of vessels in the woods 

 examined varied from 7 to 36 cm. The resistance to transverse flow through the 

 wood was found to be from 300 to 15,000 times greater than to longitudinal flow, 

 and the resistance to filtration under pressure, through a Bingle partition wall, in the 

 case of tin' wood of the crab apple, was from 2 to l<> times greater than thai to flow 

 through the entire length of the vessels. The total resistance to H« >\\ in erecl stems 

 of actively transpiring plants appears to correspond in the case of Bhrubs and small 

 tree- to a head of water of from <> to .".."> times the heighl of the plant, and iii the case 

 of large trees from 5 to 7 times their height. This would require, to maintain active 

 transpiration in tall trees, total pressures equivalent to at least LOO atmospheres. 



It appeal-, therefore, that to maintain the How a pumping action of some kind 



must be exercised in the w I. for which the presence of active living cell- i- essen- 

 tial. In support of this, it has been shown that the production of wood in a slow- 



growing tree is greater than is necessary for its mechanical requirements. There is 

 no means by which the cell- can directly pump water in a definite direction, although 

 the existence of a power of absorbing and exuding water under pressure has been 



proved in theliving wood of cul branches. It is suggested that the w l-parenchyma 



cells, by the excretion and reabsorption of dissolved materials, may bring into play 

 Burface-tension forces within the vessels of sufficient intensity to maintain a steady 

 upward flow and keep the water of the Jamin's chains in the vessel in a mobile 

 condition, ready to flow in whatever direction suction is exercised. 



It appears that the terminal branches of t ices at heights of from 22 to 44 ft. ex hi hit 

 little or no power of bleeding in the spring. It is believed possible that in such 

 trees the pumping action is only used or developed in the wood of the older stems, 

 or is only exercised w hen transpiration is active, and the water columns in t he ves- 

 sels attain a definite size in proportion to the wood-parenchyma cells. The impor- 

 tance of the Jamin's chain in the vessels is that it renders a staircase pumping action 



possible, and enables the water to lie maintained in them in a la hi le condition, ready 

 to flow to any point where moderate suction i- exercised. This pumping action 

 being diffuse and probably regulated need not produce any high pressure of exuda- 

 tion at the terminal branches of tall tree.-, and, in fact, it appears always absenl at 

 high levels. 



The artificial nutrition of diseased trees, S. A. Mokrzhetski [Zen '. Ghaz., 

 1904, Xos. 9-1S; rev. m Zhur. Opuitn. Agron. i Rum. Jour. Expt. Landw.), 6 (1905), 

 No. /, pp. 82\ 83).— The author conducted a number of experiments in which he 

 introduced arsenic, copper Bulphate, eosin, and other poisonous solutions into trees 

 for the purpose of destroying parasites, but did not obtain any very satisfactory 

 results. 



He then replaced the poisonous salts by nutritive ones and obtained interesting 

 results in improving the condition of the trees. For the introduction of dry salts 

 into the trunk of the tree holes \ in. in diameter and 1 in. deep were bored into the 

 trunk at ahout breast height Into these holes 1 to 4 gm. of salts was placed and 

 the openings covered with land plaster. For trees not over •':."> in. one hole was 

 sufficient, but for larger trees 2 to \ holes were found necessary. For trees with a 

 diameter of 7 to 9 in. pi to 12 gm. of salts was used. It was found that the earlier 



in the spring the salts were introduced the better the results. 



For different soils and under different conditions of growth the author used ferti- 

 lizing mixtures recommended by Wagner, Sorauer, and Muller-Thurgau. To tin- 

 last mixture he found it advantageous to add I part iron sulphate, to he used for 

 curing chlorosis. The experiment- showed that the dry salts diffused through the 

 trees indifferent ways, not only along vertical lines hut sometimes in spirals. The 



