308 PAIiKS AND PLEASURE-GROUNDS. 



essential to success. "We refer throughout to his ISTatu- 

 ral Orders, exhibited in his " Encyclopaedia of Trees 

 and Shrubs," as affording detailed descriptions of the 

 species. Any hardy plants recently introduced may 

 easily be inserted into their proper places as soon as 

 their respective genera and orders are ascertained. 



In connection with the genera we have indicated 

 whether the individuals are trees or shrubs, whether 

 they are deciduous or evergreen, or whether they are 

 partly the one and the other. When the genus is not 

 generally hardy, it is marked as sub-hardy ; and when 

 there are hardy and sub-hardy species in cultivation, 

 this fact also is marked. Where no such distinction is 

 made, the plants may be considered as hardy in the 

 average climate of the United Kingdom. The heights 

 specified must be regarded as the general altitude of 

 the genus rather than the stature of the individual 

 epecies ; the latter being often extremely varied, in 

 some cases ranging toward the higher, in others to- 

 ward the lower limit. Tlie numbers of species and 

 varieties are sometimes only approximative. Mr. 

 Loudon, for example, describes 170 willows, while we 

 have described only 100 ; and even that lower number 

 it woul(J probably be difiicult to procure. We believe 

 that there are about 1500 species and 1000 botanical 

 varieties of hardy trees and shrubs — exclusive of 

 what may be called florists' varieties of roses, azaleas, 

 etc. — cultivated in our well-appointed nurseries. Of 

 coui'se a selection of these is sometimes all that the 

 extent of the ground to be occupied will permit to be 

 employed. 



As many of Dr. Lindley's alliances and orders do 

 not contain plants which are ligneous and hardy, they 



