DRAINAGE ECHEVER1A 97 



very thoroughly ameliorate a heavy clay soil, in which case 

 they may be placed every 20 feet. The better the fall 

 the quicker the drain will act and the more permanent it will 

 be, as it will tend to clean itself and not fill up with silt. 

 It is important that the outlet be entirely free, and it should 

 be protected with stones or mason work. The roots of some 

 trees, particularly of willows and elms, are attracted by tile 

 drains, and often fill up the pipes. "When the drain goes 

 near such trees, therefore, it is well to cement the joints. 

 In general practice, however, the joints should not be 

 cemented, because a large part of the drainage water enters 

 at those places. In laying the tiles, it is well to cover the 

 joints with inverted sod, tarred paper, wisps of straw, 

 stones or other material. This prevents the fresh earth 

 from falling in between the joints, and by the time the ma- 

 terial is decayed the earth will have become so thoroughly 

 set that no further trouble will result. Although under- 

 drains take off superfluous water, nevertheless an under- 

 drained soil will hold more moisture than one which is not 

 drained, particularly in the case of clay lands with high 

 subsoils. This is because fine, mallow soils are ablo to hold 

 more moisture than very loose and open or very dense and 

 compact ones. A well constructed underdrain should last 

 indefinitely. 



Dutchman's Pipe. See Aristolochia. 



Echeveria. Tender succulents largely used for 

 carpet bedding and rock gardens. Echeveria secunda is some- 

 times called OLD-HEN-AND-CHICKENS, from the little plants 

 that grow out from the stem of the parent plant and show 

 around the edges of the rosette top; but the hardy Hen- 

 and-Chickens of old gardens is a different but closely allied 

 plant (Sempervivum tectorum). All the species are of easy 

 culture and thrive on sandy soil. They should not be 

 planted out until all danger of frost is over and the ground 

 thoroughly warm. Propagated by the offsets. Height 3 



