and Suburban Garde^is. 



361 



C5 



f 



on the principle explained in Illustrations ^ 

 plate II. and p. 3., near the walk. The 

 next order, being Magnoh'wcetp, forms an 

 irregular zigzag line, extending from the 

 marginal boundary to the back of the space, 

 because some of the species attain the 

 height of 30 or 40 ft. In this manner the 

 orders and tribes follow in regidar series, 

 but in irregular lines, along the margin of 

 the walks and allejs, as indicated by the 

 figures 1 to 34, ending at the latter number 

 with Tulipdcea:. 



The space occupied by this arboretum 

 is 3530 ft. in length by about an average of 

 \2\ ft. in breadth, exclusive of the central 

 and side walks and alleys ; or about one 

 and one third of an acre. The number of 

 plants exceeds 2500, being all those, ex- 

 clusive of the garden varieties of roses, 

 enumerated in the Hortus Britannicus, and 

 from twenty to thirty sorts of camellias, 

 which Mr. Donald finds will stand as hardy 

 shrubs. The spaces allowed for the trees 

 are nothing like what will admit of the 

 larger-growing kinds attaining their full 

 size ; but they are graduated on the prin- 

 ciple of taking up every plant when it 

 attains the height of 20 or 30 ft., and 

 replacing it by one of small size ; or, after 

 cutting its roots, heading it down and re- 

 planting. 



The principle adopted in ranging the 

 plants along the compartments is as fol- 

 lows : — No plant is placed nearer the cen- 

 tral broad walk than 3 ft., indicated by the 

 marginal line (g), or nearer the side walks 

 than 2 ft., indicated by the marginal line (/?). 

 All plants whose height, when full grown, 

 does not generally exceed 3 ft., are placed 

 on two lines 1 ft. 6 in. apart. ( fig. 65. a b) 

 When two, or not exceeding four, of the 

 plants of this class of heights come to- 

 gether, they are placed alternately on the 

 one line and on the other, so as that the 

 last placed plant may always be in advance 

 of the preceding one, in the direction of 

 the walk, at least 6 in. (1 2 3 4) ; but when 

 there are five, or a dozen or two, as in the 

 case of Helianthemum, the plants are placed 

 in series across the entire width of the 

 compartment (3 to 19). 



All plants which exceed 3 ft., but do not 

 exceed 6 ft., are placed on the second and 

 thii-d lines (b c), on the same principle (20 

 21 22) ; but when above three or four of 

 such plants occur, they then form a part 

 or the entire of an angular line, extending 

 across the whole width of the compartment 

 (22 to 30). 



