Analytical 



well stirred with a rod or strong spatula; the solution is 

 renewed if necessary. After washing out the solution until 

 only a faint pink colour remains, a slight excess of powdered 

 sodium bisulphite is added, and the sand is intimately mixed 

 under warm water — most effectively by using clean hands. It 

 is important that no brown stain should be left on the sand ; 

 securing its removal demands some care. The sand is finally 

 washed under a slow stream of running tap water, care being 

 taken to manipulate so that every part of the sand is washed. 

 The washing must be intimate, and need not be prolonged: 

 mere running water will not penetrate far. Most of the excess 

 of water being quickly drained off, the sand is ready for use. 

 The peas should be sparsely placed, uncovered, on the more 

 than saturated sand, and should be sprinkled with water, and 

 inspected twice daily for the first few days of germination. 



Possibly owing to the production of a volatile growth- 

 substance, a decided curliness tends to become manifest in 

 crowded pea shoots, hence a ventilated cupboard or dark room 

 is better than a closed incubator, but the temperature should 

 be maintained at about 25" C, and if small amounts of light 

 gain entry, the vessels should be turned frequently. Some few 

 of the peas are almost sure to turn mouldy ; as soon as their 

 condition is noticed, these should be removed with flamed 

 forceps, and dropped into a bath of disinfectant of low surface 

 tension. The germination cupboard should be disinfected 

 after each crop has been grown. Time for a crop, about ten 

 days. 



Those who are thinking of performing this pea test as a 

 research method will not need advice about its application, 

 but those who desire merely to make a demonstration may be 

 grateful for the hint that salt action and other effects may 

 interfere with the test. For example, the author has found 

 that after floating the split fragments of pea-stem on 20 ml. 

 of liquid in a Petri dish, there was no certain response with 

 concentrated urine, or with stale urine at any dilution. 

 Fresh urine gave the maximum response of which it was 

 capable — not, of course, the maximum of Went's scale — when 

 about 4 ml. were diluted to 20 ml. Here, however, is a dislocat- 



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