DISEASES OF TREES PRODUCED BY INSECTS. 



25 



stripping the trees bare. After injury by the nun caterpillar the trees 

 seem to suffer most in the second year following the damage. 



The new growth of the fir generally sends out only very short needles, 

 which remain as brush shoots (Fig. 3.) In the pine there arises after 

 defoliation from lateral buds " rosette shoots," i. e., very short, persist- 

 ing growths bearing dense, short, broad, and serrate (gesagte) single 

 needles (Fig. 4). But on the other hand cases occur, when many buds 

 are destroyed, where the remaining remnant of the entire sap-stream is 

 used and the organs formed out of it, i. e., needles or leaves become 

 unusually large, as for example in the ordinary pine, in which case the 

 leaves bear three needles. 



Fig. 3. Lateral twig of a fir eaten by nun cater- 

 pillars in 1856. which in 1858 only produced 

 " brush needles." After Katzeburg. 



Fig. 4. 



Kosette shoot on the pine. After 

 Ratzeburg. 



Similar relations are observed in the helve oak attacked by Orchestes. 

 Generally the first growth seems to grow straight on and resist the in- 

 jury arising from the laying of the eggs by the female of this leaping 

 weevil, and the injured leaves are crumpled, but such leaves on the 

 Johannis growth (Johannistriebe) become unusually large and abnor- 

 mally formed, while those situated on the summit entirely assume their 

 normal shape. 



The origin of repaired parts from representative indefinite groicths is 

 very general. — The clearest example is afforded by pines deprived by 

 Retinia buoliana of their terminal shoots. In this case there grows out 

 after a certain time a shoot of the uppermost hniiich (Quirles), which 

 now becomes the terminal shoot, though in growing up there is a crum- 

 bling of the stem in the place under consideration. 



For the formation of mostly abnormally shaped organs which have 

 been replaced from sleeping buds, the pine affords the best example. 

 From the usually dormant sheathing-buds on the point of origin of the 

 short shoot occurring between every two pine needles, are developed 



