42 



EXPERIMENTS WITH PLANTS 



drying up but prevents them from being washed away 

 in watering. In watering small seeds where no such 

 covering is used, a cloth may be laid over them or 

 water may be applied to the soil from below (by set- 



f{ 



!<? 



ting the box ov pot in water for a short 

 time) . 



Is it possible to prevent germination 

 by keeping the soil too wet (i. e., by 

 excluding air by water) ? Would a reser- 

 voir of air in the seed be useful in very 

 wet soil ? Peanuts and Castor-beans are 

 said to rot in wet soil if their coats be 

 removed, but not otherwise; do you see 

 why this may be true! Try planting 

 them (with the coats both off and on) 

 in pots of earth which are allowed to 

 stand in pans of water. 



How does the seed absorb warmth? 

 Is the seed -cover a hindrance in this 

 respect also? Seal the bulb of a ther- 

 mometer into a seed- cover, as shown in 

 Fig. 37 (first removing the contents of 

 the seed) . Place this, together with a 

 naked thermometer, which has first been 

 carefully compared with it, on the surface 

 of the soil in sunlight (thus imitating 



37. Method of testing thc couditlou of a sccd so placed) ; take 



the permeabihty or a / / 



the seed - cover to 



heat. 



readings every ten or fifteen minutes. 



