170 THE GARDEN OF EARTH 



They are a disease of the Oak-tree. Such gall-growths 

 are found on other plants as well, and they are usually 

 due to a small living creature getting inside the stem, 

 or branch, and staying there, while an unhealthy lump 

 forms round it. 



Often we see upon the trunk of a tree a large unsightly 

 swelling, and this again means disease. With a tree, 

 happily, it does not mean pain, as any such growth 

 would with a man, but it does mean that the health of 

 the tree is not what it should be. 



One well-known parasite is an odd little red plant, 

 called the " Dodder," which goes creeping over others, 

 sucking its food from them, and never taking the trouble 

 to send a root into the earth. One may often see the 

 Dodder crawling over bushes on a common. 



And though usually we look on such parasites as 

 hurtful to the plants upon which they fasten, yet it 

 may not be so in every case. For, with regard to the 

 " galls " just mentioned, it has been found, curiously, 

 that in growing thus they have sometimes caused the 

 single flowers of the plant attacked to become double ; 

 the stamens altering into petals. You know how the 

 single flowers of a Wild Rose may become double through 

 cultivation. Here the same thing is believed to come 

 about, not through a gardener's care, but through that 

 which is more in the nature of a disease. 



And this does not stand alone. A botanist, who 

 studied the matter closely, found in certain instances 

 that a parasite, preying on the roots of a plant, instead 

 of doing it harm seemed actually to do it good. The 

 plant which was preyed upon, far from being weakened, 

 grew more strong and healthy. 



