METABOLIC PROCESSKS IX THE PLANT. 321 



calculated. The soaking of the seeds, the culture of seedlings, 

 and the determination of the weight of dry substance in these are 

 made as described in connection with the experiments concerning 

 the value of free atmospheric Nitrogen for plants (see 19). The 

 seedlings mnst naturally, however, be developed in complete 

 absence of light, e.g. in a cupboard, and need not be placed under 

 bell-glasses for development. 



The chief difficulty in the researches is to obtain uniform seed- 

 ling material. If we lay out a number of seeds to germinate, it 

 very often happens that many of the seedlings develop vigorously, 

 others feebly, while some ma.y not germinate at all, and decay. 

 In many cases, however {e.g. with wheat or peas), we shall be 

 sure to find in a number of cultures some which are thoroughly 

 satisfactory, in which, viz., all the seeds employed have yielded 

 seedlings approximately uniform in development, and that is, of 

 course, the most favourable case to be expected. If we use small 

 seeds (rape, poppy), which, after being soaked on pieces of pumice 

 stone, lying in water, it is best to germinate on moist filter paper 

 or moistened glass wool, it is advisable to count the seeds, and 

 calculate the average weight per seed. The seeds which do not 

 germinate are counted, and we deduct their original weight from 

 the total weight of seeds taken. If the number of seeds ger- 

 minating badly, or not at all, is not too great, this method does 

 not lead to excessive errors. In researches with large seeds 

 (varieties of beans), it is preferable to deal with each separate 

 object by itself. Each single seed is separately weighed, soaked 

 and germinated on moistened glass wool, and then "the develop- 

 ment of each separate seedling is continued in a separate glass, 

 containing distilled water, in the manner described for water 

 cultures (see 1). Many little precautions, which are nevertheless 

 of importance to ensure our obtaining seedlings suitable for our 

 purpose, will readily occur to us in carrying out the experiments. 



In comparative work on the relation between the metabolic 

 processes and conditions of temperature, the seeds must naturally 

 be germinated in thermostats (see 77) kept at different tempera- 

 tures. 



P.P. 



