134 Principles of Plant Culture. 
sity to plant culture in arid regions, and may be profitably 
employed at certain times in the great majority of seasons, 
in very many localities where the annual rainfall would 
satisfy the needs of crops, were it more uniformly distributed. 
235. Drying, beyond a certain limit, Kills Plant Tis- 
sues by destroying, in part, their power for conducting 
water. Care must always be used to retain the normal 
moisture in buds (394), cuttings (358), and cions (386) and 
in the roots of plants lifted for transplanting. 
Section II]. Tue Puant as AFFECTED BY UNFAVORABLE 
Licut 
A— By Excessive Licut 
236. The Unob- 
structed Rays of the 
Sun are often Injurious 
to young seedlings, to un- 
rooted cuttings and to 
plants recently trans- | 7 
planted. It is difficult to = 
separate the influences of 
light, and heat, since the 
heat is usually greatest 
Fic. 60. Lath screen used for shading cold- 
: frames, and tender plants in the open ground. 
where the sun’s rays are (After Bailey). 
brightest; but bright light 
probably stimulates 
transpiration (75), inde- 
pendent of heat, and thus | 
tends to exhaust the plant 
of water. Various devices Fia. 61. Shed screen built of three-inch 
are used to break the force Wide slats, for shading tender plants and for 
storing pots and boxes of slow-germinating 
of the solar rays. In out- seeds, (After Bailey). 
