INJURY TO THE LARCH BY SAWFLY 



LARVAE 



By MAUD DeWiTT PEARL 



PROFESSOR A. G. HARPER, suited in a lessening in the amount of 

 of Oxford, England, has re- growth of the annual ring and in a de- 

 cently published the results of crease in the thickness of the walls of 

 a most thorough investigation the cells forming the so-called autumn 

 of the harm which Sawfly larvae do to wood. The decrease in ring growth 

 the larch. This pest first made its on- was more noticeable at the base of the 

 slaught upon larches in England in tree than at the tip, as would be ex- 

 1904, attacking not only the European pected. In cases of severe attacks ot 

 larch but also species of the Japanese the larvae it was found that cambium 

 larch, which had recently been intro- growth ceased entirely in pertain parts 

 duced into England. Most of the trees of the tree, particularly near the base, 

 investigated had suffered defoliation The width of the ring of autumn wood 

 during several successive years. was not always lessened, but the outer 



In order to study very accurately the cell walls of this ring failed to thicken 

 extent of injury wrought by defoliation, while the inner walls presented a normal 

 a cross section from each tree was taken appearance. The cause of this differ- 

 regularly, every four or five feet apart, ence between the walls of the outer and 

 depending upon the tree, from the base inner cells is not perfectly clear. Pos- 

 to the top. A rectangular piece, from sibly the starvation which the tree suf- 

 8 to 12 mm. broad, was cut out of the fers through defoliation causes an ar- 

 circumference at the four points of the rest of the development of the cells, 

 compass, the north side of the tree On the other hand there is an indication 

 having been marked previous to cutting, that in some cases the second growth 

 A thin layer was cut from each one of of leaves which the tree very often 

 these blocks for microscopical examina- puts out after being attacked by the 

 tion and measurement. Three separate larvae might possibly be the cause of 

 sets of measurements were made for the thin walls. The growing leaves 

 ring growth and development of the draw heavily upon the water supply 

 autumn wood on each layer, so that, in and conditions at this time are similar 

 all, twelve measurements were taken to those in early summer when the 

 for every cross section. The average regular leaf growth occurs and the so- 

 of these measurements was taken as an called spring wood, whose cells have 

 indication of the mean radial enlarge- thin walls, is formed, 

 ment of the tree at a particular height. Another condition which results 



The investigation showed that de- through defoliation is the formation of 



foliation and consequent starvation re- abnormal resin ducts. 



Red Alder for Clothes Pins. 



Manufacturers have found that red alder from the Pacific coast is a suitable material for 

 clothes pins. Alder makes a white, smooth, springy pin. As a result of this fact, a clothes 

 pin factor}-, said to be the first on the Pacific coast, may be established at Portland, Oregon. 



Best Sight of Forest Fires. 



It is said that the best times of day to see forest fires from lookout stations are just 

 after daylight and just before sunset. 



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