296 FOREST ENTOMOLOGY. 



pests, having regard to recognised systems of " mixing " with those 

 very trees which act as host-plants in the alternation of the species ? 

 Much has yet to be learnt from good sylvicultural conditions, careful 

 work in planting Avith well-rooted plants, and also from experiment 

 and observation. Take, for example, a suggestive case in point — viz., 

 the growing of young silver firs. On many estates very fine examples 

 of old silver fir trees can be found, and the modern forester with his 

 high-class sylviculture cannot grow it. Without giving any definite 

 opinion, much might be done in the younger stages by growing under 

 shade of hardwoods in the nursery — say, plant a row of hardwoods, 

 two or three rows of silver fir, and aojain a row of hardwoods, and so 



Fig. 280. — Hibertiatinij winter forms of four s^Kcics o/Chermes. 

 , C. (tbietis ; b, C. strobllobius ; c, C. coccineus ; d, C. siliricus; together with a highly 

 magnified single chitin plate of each species. Copied from Judeich and Nitsche. 



on throughout the nursery plot.^ Perhaps, also, an exception may be 

 made to the general rule of much transplanting in the nursery. This 

 tree should not be too often moved, but plants should be specially 

 carefully taken up when they are lifted. Again, when transplanted 

 in the forest, the silver firs should not be planted in the open, but as 

 shade-bearers in late filling up, or otherwise solely as under-planting. 



Then as regards the injurious effects of C. viridis as compared with 

 C. strohilohius, it may be said, so far as real injuries are concerned, 

 that the former is often injurious in the nursery-lines, more especially 

 to those plants standing in the rows for three consecutive years, and 



^ I have found that Silver fir plants grown in this manner were free from 

 Chermes, whereas plants of a similar age grown in the open in the same plot 

 were killed outright \>y Chermes. 



