746 EXPERIMENT STATION EECORD. 



"(2) What inllneuce does fruit bearing exert upon the lignitication of cell walls? 

 "(3) Does the fruit-bearing shoot contain any supplementary mechanical tissue 

 formed to supply a possible lack of developmeut in the xylem cylinder?" 



The study of the material seemed to warrant the following conclu- 

 sions : 



" (1) The 1-year-okl fruit-bearing shoots of the apple and the pear have less wood 

 'n proportion to their diameter than tlie vegetative shoot of the same age. This 

 is due in the apple largely to an increase in the cortex and in the pear solely to a 

 great increase in the cortex and the pith of the fruit-bearing shoot. It does not 

 appear, however, from the structure of the shoots, that the fruit-bearing shoot is 

 weaker than the vegetative. The former is well supplied with supplementary me- 

 chanical tissue, which is distributed at those points where it is most needed, and 

 thus gives it an increase of strength for the fruit-beariug year which i'ully makes up 

 for the diiierenco in xylem developmeut. 



"(2) In the i)each the fruit-bearing shoot has more wood than the vegetative 

 shoot, and the walls of the wood cells are as thick in the former as in the latter. 



"(3) In general il- may be said that the effect of fruit bearing ujion the tissues is 

 local. In the apple and pear it is perceptible throughout the 1-year-old shoot; in 

 the plum and peach it is confined to a small area in the immediate neighborhood of 

 the fruit stalk. 



"(4) The local effects of fruit bearing tend to an increase of cells, with a decrease 

 in the thickness and lignification of the walls of the wood cells. The cortex is 

 especially enlarged, giving rise in the apple and jiear to the swollen condition of the 

 fruit-bearing shoot. 



"(5) In all cases the increase in growth is greatest on the side near the fruit 

 stalk, although the wood in the apple and pear is best developed on the side of the 

 lateral vegetative bud. 



"(6) The local effect of fruit bearing on the wood cylinder disappears with time. 

 The study of apple shoots that had borne fruit during their first year showed that 

 in the 2 or 4 years following there had been a rapid increase of wood, especially on 

 the side of the fruit scar. This side was weakest at the end of the first year. Tliese 

 shoots at the end of 3 and 5 years had a better xylem developmeut than shoots of 

 the same age that had never borne fruit. 



"(7) Fruit bearing has a temporary local eftect upon the lignification of the walls 

 of the wood ceils. It prevents their lignification, wholly or in part, according to 

 their distance from the fruit stalk. The lignification of other cell walls is promoted 

 by fruit bearing. In the fruit stalk the greatest i)art of the tissue has become 

 lignified, and in the upjier part of the apjile and pear shoots there is an abundance of 

 well lignified sclerenchyma and hard bast, which is either not found in the vegetative 

 slioot or only sparingly so." 



Respiration of -wounded plants, H. M. Richards {Ann. Bot, 10 

 (1896), JVo. 40, pp. 531-5x2, figsi. 2). — The investigations of Bohm^ and 

 Stich^ have shown that there was a considerable rise in the amount of 

 carbon dioxid produced by potatoes when injured in various ways. In 

 a subsequent note Bohra^ gives as a possible explanation of the 

 increased respiration, a traumatic action of the wound, the organ not 

 depending upon the action of the atmospheric oxygen on the tissue. In 

 order to arrive at some definite conclusion regarding this subject the 

 author conducted an extensive series of experiments with potato tubers, 



1 Bot. Ztg., 45 (1887), p. 671. 



2 Flora, 49 (1891), p. 1. 



3 Bot. Centbl., .50 (1892), p. 200. 



