156 STATE HORTICULTURAL SOCIETY. 



seasons. Practically, however, many people believe that the great use of 

 the trees is to serve as supports for telegraph wires, as ladders for tele- 

 phone workmen, or as convenient places for fastening horses. In short, 

 that a tree should be so treated that it may develop a symmetrical form 

 and luxuriant foliage is nobody's business, while, on the other hand, it is 

 assumed that it is the right of every one to fasten his horse to any tree he 

 pleases or to use the branches as supports for wires. The march of 

 improvement, as it is called, never respects the trees. If a sidewalk is to 

 be widened, down go the trees, or their roots are chopped off in such a 

 way as to injure them. If some enterprising man wishes to build a new 

 house on the site of an old one, the old house is sold for a song and is 

 moved off to some distant part of the town, being dragged along through 

 narrow streets crushing and maining the trees on the way, just as if these 

 public ornaments were of no account compared with private gain. In fact, 

 it sometimes seems as if a good many people believed that one could not 

 do anything to a tree which really would injure it, and that a tree is so 

 constituted that it can grow on in spite of all obstacles. 



We should begin by recognizing that a tree is a living thing which is 

 not only readily affected by the soil and atmosphere, but is also sensitive 

 to mechanical injuries to a degree which might not at first be suspected. 

 An animal tells us by its actions when it has been injured. We know the 

 injuries done to trees only by the after effects, which may not be evident 

 for months or even a few years, and it is my special purpose today to call 

 your attention to some of the injurious effects which follow mechanical 

 injuries. The subject is rather complicated and implies some knowledge 

 of the microscopic structure of trunks and branches, but I shall endeavor 

 to avoid technicalities as far as possible. 



Before we can understand the harm done by mechanical injuries we 

 must first consider briefly the normal structure of the trunk. If we exam- 

 ine with a microscope a cross-section of a very young twig, we find that the 

 surface is composed of a single layer of thin, colorless cells called the 

 epidermis, beneath which are several layers of larger cells, many of which 

 contain green coloring matter. Then come the vascular bundles arranged 

 in a ring, although they are not really in contact with one another but are 

 separated by what we may call the rays, which pass from the pith to the outer 

 green cells, and are composed of cells not unlike the latter in shape, that is 

 spherical or polyhedral, or some simple modification of these forms. A 

 longitudinal section through the vascular bundles shows that the cells of 

 which they are composed are, in great part, very much elongated, so that 

 they may be called fibres, ducts, or vessels. When seen in cross-section, 

 each vascular bundle is wedge-shape and, if carefully examined, is found 

 to consist of an outer and an inner part; that is, in respect to the circum- 

 ference of the tree. The inner portion develops into the hard wood of the 

 stem, while the outer part becomes a portion of what, for want of a better 

 expression, we may call the inner bark, or blast. Between the outer and 

 inner parts of the vascular bundle is a thin layer of small, colorless, brick- 

 shaped cells, the cambium. The cambium is the most important part of 

 the stem, since its cells during the season of growth are constantly forming 

 new wood cells on the inner side, while those on the outer side are forming 

 new cells of the inner bark. Tb.3 cambium itself does not vary much in 

 thickness at different ages and, extending continuously throughout the 

 length of the stem, forms the circumference of a cylinder whose diameter 

 increases from year to year. It is important to bear in mind that it is 



