EVERGREENS. 



100 



EXOGEJfS. 



They will grow in any common garden 

 soil, and the annuals should he sown 

 in March or April, as, though they are 

 natives of California, they are not in- 

 jured by heat. 



Evening Primrose. See Oeno- 

 thera. 



Evergreens. — No garden should 

 be without its due proportion of ever- 

 greens ; and these plants are still 

 more essential in small gardens than 

 in large ones. Their advantages are, 

 that they afford a screen to secure 

 privacy in winter as well as summer; 

 that they preserve an appearance of 

 verdure at all seasons ; and that they 

 do not disfigure the walks by falling 

 leaves, which, where there is no re- 

 gular pardener, render it very difficult 

 to keep a place neat. They are also 

 very useful in affording a rich back- 

 ground to those ornamental trees and 

 shrubs which produce their flowers 

 before their leaves ; suck as the double- 

 blossomed Peach, the Almond, the 

 Snowy Mespilus, and Magnolia Con- 

 spicua. It is the want of evergreens 

 that gives the gardens in the neigh- 

 bourhood of Paris, and most of the 

 other continental cities, such an air 

 of meagreness and poverty. But it 

 cannot there be remedied, as few 

 evergreens will resist the cold of their 

 winters. This may appear strange to 

 those who have experienced the heat 

 of the continental summers ; but the 

 fact is, that their winters are as much 

 colder than ours as their summers are 

 warmer, and thus the average heat of 

 the year is nearly the same. Alter- 

 nate seasons of great heat and cold are 

 favourable to deciduous plants, as the 

 heat ripens their wood, and the cold 

 gives them a season of complete re- 

 pose when they have lost their leaves ; 



but a moist temperate climate like 

 that of Britain is more suitable to 

 evergreens, which continue in a grow- 

 ing state nearly all the year. 



In street gardens, besides the ever- 

 green trees and shrubs, it is advisable 

 to select a few evergreen herbaceous 

 plants, such as Pinks and Carnations, 

 Wallflowers, &c, to give an agreeable 

 effect to the beds during winter, when 

 they are devoid of flowers. 



Evergreen Thorn. — The Pyra- 

 cantha. (See Crat;e x gus). 



Everlasting. — See Gnapha n lium 

 and Helichry'slm. 



Everlasting Pea. — See La'thy- 

 rus. 



Exogens. — Dicotyledonous plants. 

 The exogenous plants have received 

 their name because the new wood of 

 their trees and shrubs is deposited on 

 the outside of the old wood, one 

 layer being deposited every year. 

 Thus the age of a tree may be counted 

 by the number of its layers, shown by 

 its wood when the trunk is cut down. 

 The soil in which the tree was grown, 

 and even the weather in the different 

 years, may be guessed in the same 

 manner ; as the layers of trees grown 

 in rich valleys are much thicker than 

 those of trees grown in poor soils on 

 mountains ; and the layers deposited 

 in damp cold summers are thicker than 

 those of dry, warm seasons. When 

 trees have grown in a wood, with one 

 side of the trunk fully exposed to the 

 sun, and the other shaded by the other 

 trees, a difference is very perceptible 

 in the layers. Exogenous trees have 

 medullary rays and reticulated leaves. 

 All the forest trees of Britain and 

 other temperate climates belong to 

 this class. 



