The Science of Plant Growing 



27 



of any importance to cultivators in this country. All fertile soils swarm 

 with minute, one-celled fungi or microbes, living upon dead matter and 

 converting much of it into a soluble form, suitable as food for green plants. 

 In a word, they are the agents alike of decay and fertility, preparing the 

 soil, the manure, and leaf heaps for the use of the higher plants. 



Lichens are composite plants, consisting of a fungus and a small green 

 alga, working in co-partnership for their mutual benefit. Even some of 

 the higher plants, including several forest trees, have messmates or co- 

 operators amongst fungi, large enough to be seen by the naked eye 

 (fig. 10). The fungi closely invest the fibrous ends of the roots and absorb 

 the food they require from the trees. On the other hand, some of the 

 waste products of the fungi 

 are required by the trees to V^M* 1 



complete their bill of fare. 

 It is not yet determined to 

 what extent this co-operation 

 prevails among cultivated 

 plants, but some plants diffi- 

 cult to cultivate may really 

 require this kind of assist- 

 ance. It is well known that 

 Rhododendrons and other 

 plants belonging to the same 

 family like a peaty soil and 

 hate lime in any form. In 

 all probability the lime de- 

 stroys the microbes in the 

 peat that are essential to the 

 welfare of the Rhododen- 

 drons. 



Desert Plants. Echeverias, Crassulas, and Aloes, from South Africa 

 and Mexico, have fleshy stems and leaves. Cacti, including Epiphyllums 

 from Brazil, Mamillarias and Phyllocacti, from Mexico and other warm 

 and dry parts of America, are also fleshy but have dispensed with leaves 

 to economize their liquids. In their native habitats they get very little 

 rain, and make a point of storing up what they do get, while their struc- 

 ture is such as to prevent the liquids from escaping too freely. Under 

 cultivation many of them enjoy liberal treatment in summer, when the 

 temperature is high and they are making their growth, but they must 

 be kept relatively dry in winter when at rest and the light is bad. With 

 few exceptions they like a relatively high temperature even in winter. 

 They cannot give off moisture like thin-leaved, green plants, consequently 

 water must be withheld almost entirely during winter, otherwise they 

 would decay wholesale. A gardener can readily diagnose a plant of this 

 character, without knowing its name or from what country it comes, and 

 give it the proper treatment accordingly. 



Fig. 10. Illustration of Co-partnership or Symbiosis 



1, Roots of the White Poplar with Myeelial covering. 2, Tip 

 of a Root of the Beech with closely adherent Myeelial covering ; 

 x 100 (after Frank). In these cases the Myeelial threads on 

 the roots are of fungous origin, deriving nourishment from the 

 roots on which they grow, but at the same time supplying 

 food material to the roots. 



