CONTRIBUTIONS FROM THE WISLEY LABORATORY. 307 



first, which was used in all the pot experiments (referred to as Series 1 

 below), and the next two, which were used in the experiments in the 

 open (Series 2 and 3 below). The first was rather brown in 

 colour, contained a considerable quantity of water (over 60 per cent.), 

 and was of rather rough texture ; i.e. the pieces of which it was com- 

 posed varied a great deal in size. The next two were almost black, 

 contained less moisture, and had apparently been riddled before 

 being sent out ; on this account it was much easier to sow evenly 

 on the ground than the first lot would have been. It is scarcely to 

 be doubted that the difference in colour denoted a difference in chemical 

 composition, and it is probable the drying process may have brought 

 about some difference in composition too. Water extracts of both 

 forms gave a decidedly acid reaction. The last (used in Series 4 and 5 

 below) received in 1915 was browner than these. No analysis of any 

 of the samples was made. 



It seems apparent that Professor Bottomley is still experimenting 

 with the material, and has not yet settled upon a fixed product or a fixed 

 method of preparing it, so that whatever conclusions are drawn from 

 the results of the following experiments can apply only to the particular 

 samples used, and are not of general application. It is to be regretted 

 that we were unable to use the same quality of bacterized peat in 

 all the experiments, as the results of the different series are not now 

 directly comparable with one another, and more especially as one 

 point of considerable interest in such a trying season as that of 1914 

 is involved, viz., the part played by water in rendering available the 

 constituents of the treated peat. 



D. — Design of the Experiments. 



It seemed desirable to ascertain as far as possible whether the 

 alleged acceleration of growth was due to : 



1. The water-holding capacity of the peat, or 



2. The salts, and especially the nitrogen it contained, or 



3. The action of hypothetical accessory " food-bodies," which 

 may be called activators. 



The last point may be dismissed in a few words. None of the 

 experiments gave any evidence for or against the theory of the presence 

 of such bodies, and comparative experiments carried out in soil are 

 unlikely to do so, for the following reasons. If the same amount of 

 nitrogen is added in farmyard manure or in other organic mixtures, it 

 is not at all clear that the hypothetical accessory food bodies will not 

 also be added. If it be added in the form of nitrate of soda or other 

 salt, this may well cause chemical changes to occur in the organic con- 

 stituents of the soil and lead to the formation of these accessory 

 bodies (assuming such to exist). Too little of the subtle chemistry 

 of the soil is known for it to be safe to theorize concerning these 

 bodies from the evidence obtained from experiments such as those 

 to be detailed immediately. 



