52 MY GARDEN. 



Guano contains much ammonia with phosphates, as it is the drop- 

 pings of sea-birds, which have accumulated on barren rocks for ages. 

 We only employ it to a small extent, and then chiefly when we 

 desire large onions. Guano is injurious to strawberries, causing the 

 plants to run to leaf; and on the whole it had better be discarded from 

 the garden, in favour of good stable manure. 



I have employed woollen materials. When laid upon the surface 

 of a pot, containing a fruit-tree, it keeps the earth moist. After a 

 little time the roots form in it, and the whole becomes one tangled 

 mass of rootlets. The wool rots, and the roots then become exposed, 

 and are in the end destroyed by frost or drought. 



When I saw this extraordinary result I forbade its use, but under 

 certain precautions no doubt it may occasionally be profitably 

 employed. 



There appears to be an exception with respect to epiphytic plants, 

 or plants without roots, which live on other plants. Take for example 

 the dodder, which lives on clover and heath plants. These plants, 

 however, twist round other plants, and hug them so closely, that the 

 cells of one species come in direct contact with the cells of another. 

 By this absolute contact of cells the salts are able to pass from one 

 plant to the other, according to Graham's law of Dialysis. Professor 

 Graham worked out the law of Dialysis, and separated all bodies 

 into colloids and crystalloids. The first such as gum and starch do 

 not readily pass through animal membranes. The second, or crystal- 

 loids such as alkaline salts pass through a layer of membrane imper- 

 vious to water, as though it had no existence, 



By this means a rapidly growing epiphytic plant encircles with its 

 fatal embrace another plant, and pumps out by dialysis all its salts. 

 Th.e close manner in which the epiphyte attaches itself is well seen 

 in a very curious plant brought from Chili by the missionaries, called 

 Cuscuta reflexa, which lives upon the ivy and many of our green- 

 house plants. A fine specimen was given to me by my friend Mr. 

 Terry, and it is most interesting to see how firmly it attaches itself 

 to the leaves and stems of other plants. 



