290 ANNUAL OF SCIENTIFIC DISCOVERT. 



of chlorophyll were attached to the walls which separate the 

 cells from one another; there were none on the upper or under 

 walls which form the surfaces of the leaf. Under the influence of 

 light the grains change their position from the lateral to the super- 

 ficial walls, the movement taking place, under favorable circum- 

 stances, in about a quarter of an hour. On attaining their new 

 position, the grains do not remain entirely immovable, but con- 

 tinually approach and separate from one another. If again dark- 

 ened, they leave their new position, and return to the lateral 

 walls. Artificial light produces the same effect as daylight. A 

 protoplasmic material is intimately associated with the grains of 

 chlorophyll, causing them to move in masses of net-work rather* 

 than in isolated grains ; and this protoplasm is supposed to be the 

 vital and animating part of the cell. Quarterly Journal of Science. 



GIRDLING FRUIT-TREES TO MAKE THEM BEAR. 



A correspondent of the "Boston Journal of Chemistry" states 

 that there is no doubt that the girdling of fruit-trees is a cause of 

 abundant fruitage ; but it by no means follows from this fact that 

 a general principle can be deduced, that trees would be improved, 

 or the crop increased for a series of years, by such treatment. It 

 is well known that gardeners frequently girdle a branch, by re- 

 moving a narrow ring of bark around it, when they wish to in- 

 crease the size and beauty of the fruit; but it is done at the 

 expense of its vitality, and, unless the operation is skilfully per- 

 formed, will invariably destroy it before the season of bearing the 

 next year. 



The crude sap, taken up from the soil by the roots of the tree, 

 ascends principally through the vascular tissue of the alburnum 

 or sap-wood to the leaves of the branches, and there both this and 

 the carbon of the carbonic acid, absorbed from the air by the 

 leaves, are organized into the proper substance for the growth of 

 the wood and fruit. It then descends on the outside, principally 

 through the sieve tissue of the cambium layer, forming a new 

 layer of wood and bark ; while a part also goes to the nourishment 

 of the fruit. If there is no obstruction of the elaborated sap in its 

 downward course, it is equally distributed to the branches, fruit, 

 stem, and roots ; but if the bark and cambium layer are removed 

 by girdling, it is stopped in its descent, and consequently received 

 into the branches and fruit in excess, and they are thus increased 

 at the expense of the part below. In this way we account for the 

 increase of the fruit by girdling. 



Professor John Linclley, when speaking of this subject in his 

 late treatise on horticulture, quotes Mr. T. A. Knight approv- 

 ingly, as follows : " When the course of the descending current is 

 intercepted, that naturally stagnates, and accumulates above the 

 decorticated space, whence it is repulsed and carried upward, to 

 be expended in an increased production of blossoms and fruit." 

 This theory is adopted by the best physiologists of the present 

 time, and can be demonstrated with almost mathematical cer- 



