3 io BRITISH FOREST TREES 



better and more easily attained by breaking out the side buds, 

 and thus interfering with the development of lateral twigs, in 

 consequence of which the growth in height is naturally greater. 



4. ASPEN (POPULUS TREMULA, L.) AND POPLARS 

 (POPULUS). 



Of the genus Populus, of which eighteen distinct species in 

 Europe now occur, including the Aspen or trembling Poplar 

 (P. tremula, L.), the Black Poplar (P. nigra, L.), the Silver, 

 white or Abele Poplar (P. alba, L.), the Grey or common 

 White Poplar (P. canescens, Sm.), and the Lombardy or 

 Pyramidal Poplar (P. pyramidalis, Roz.), the aspen is the 

 only species which can properly be regarded as of sylvi- 

 cultural value ; and even it was long considered rather in 

 the light of a weed than an object worthy of sylvi- 

 culture. More recently, however, their beauty as ornamental 

 trees, the useful qualities of their bark for tanning, and of 

 their timber for the manufacture of packing-cases, matches, 

 cellulose for paper-pulp, &c., where the use of a soft, light 

 wood is desirable, their ready growth along the banks of 

 streams, canals, ponds, and similar localities, which they are 

 called on to share only with their near relatives the willows, 

 or sometimes the elm, and their extreme productiveness, all 

 speak for their cultivation where feasible. According to 

 Burckhardt, 1 



"In rapidity of growth the poplars, especially the class of black 

 poplars, outrival all other species of trees, and it often happens that 

 the aged landowner reaps as large-girthed, valuable timber, what he 

 planted out as a 'young man." 



Their easy and cheap propagation by slips has considerably 

 helped on the distribution of the species introduced into 

 1 Stien unit Pflanzen, 1871, p. 450. 



