48 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



Commission is used as a general available source of data, and 

 without any intention of criticising the data given or the value 

 of the work for the purpose of which it was in the main under- 

 taken, it is obvious that so far as this Bulletin goes no pretence 

 was made to study in detail soil conditions as they affect the 

 species measured, since only soil structure is mentioned, and 

 that only in a general way. Therefore no deductions upon 

 which reliance can be placed are possible as regards the soil 

 conditions necessary for the growth of these species. For 

 example, the observation " the absence of any clear indication 

 as to the effect of soil upon quality class," is apt to mislead if not 

 taken at its true value that soil structure in itself has no effect 

 upon the growth of larch, a remark which might apply equally 

 well to almost any tree. The important factor of soil aeration 

 is entirely neglected, except in so far as it may be deduced on 

 the average from structural data, so that from the number of 

 plots investigated the soil conditions observed are wholly 

 inadequate for any conclusion to be drawn. The clays and 

 clay-loams are sufficiently small in number, compared with the 

 more typical larch soils, to be considered in the light of 

 exceptions ; shallow clay on a rock bottom, for example, with 

 a good slope and therefore rapid water movement might 

 produce conditions of aeration and soil moisture similar to 

 loam, but, of course, no real cause can be given without data 

 from the actual area. The example is used to show that no 

 statement with regard to soil as a factor of locality is possible, 

 unless sufficiently intensive soil data are known. On the other 

 hand, the more extensive data included in the remark that 

 "larch has almost invariably been planted on deep soils" (all 

 except 3 per cent, of the plots measured) make the observation 

 of somewhat suggestive value, since on soil types where no 

 larch is found there is good reason to believe it will not grow, 

 when one considers how varied are the conditions under which 

 it has been attempted to grow larch; and "depth of soil," at 

 least reduced to its moisture equivalent " stable water-aeration 

 conditions through the growing season," is essential to larch. 



The accumulation of the mass of data thus shown to be 

 necessary is a task of the greatest magnitude, requiring many 

 years for its accomplishment, and as such ought to be undertaken 

 immediately if it is to be of any value even to our proximate 

 successors. The length of time necessary for its full accomplish- 



