35 



you cut them clean down to the place from which they were pro- 

 duced, otherwise that part of the branch which is left will also 

 decay and prove hurtful to the tree. 



RADIATION is the spreading of heat, which arises from heat 

 passing from a hot body to a cooler one near it. The spreading of 

 heat takes place between the surface of the ground and the air 

 when the air is cold : though the soil be warm it soon loses its 

 heat, and dew or hoar frost is formed on the ground, or grass, 

 by the moisture diffused in the air. But when the sky is co- 

 vered with clouds, the spreading and loss of heat is in a great 

 measure prevented, and hence there is no dew or hoar frost 

 found on a calm cloudy night. Hence the use of protecting 

 plants by a covering of matting, which stops the heat of the soil 

 from spreading about and being lost in the air, 



REPRODUCTIVE OKGANS are those parts of a plant which are 

 essential to its propagation ; they include the flower, with its 

 immediate accompaniments, or peculiarities, the flower, stalk, 

 receptacle, and inflorescence, together with the ovary or fruit. 



RUNNERS are young shoots issuing from the collar or summit 

 of the root, and creeping along the surface of the soil, but produc- 

 ing a new root, and leaves at the extremity, and forming a new 

 individual, by the decay of the connecting link, as in the straw- 

 berry. 



SAP is taken up by the tip of the roots, fibres, or spongelets 

 and carried into the interior of the stem, and although thin and 

 clear at first, becomes thicker as it ascends in the plant. 



SOWING is the first operation of rearing ; when seeds are de- 

 posited singly, in rows or beds, they are said to be planted. When 

 dropped in numbers together, they are said to be sown. The opera- 

 tion of sowing is either performed in drills, patches, or broadcast. 

 In broadcast sowing, the seed is scattered over a breadth of surface 

 previously prepared by digging or otherwise, minutely pulverised. 

 The seed is taken up in the hand and scattered regularly over 

 the surface, so as to fall as equally as possible. A windy day is 

 particularly to be avoided. Dry weather is also essentially neces- 

 sary for sowing, more especially for covering in the seed. 



SPURIOUS PEATY SOILS. Lakes and pools of water are sometimes 

 filled up by the accumulation of the remains of aquatic plants, and 



