4 i2 SCIENCE PROGRESS 



the total weight of the crops and the average size of the fruits 

 but these data must be supplemented with others less dependent 

 on climatic peculiarities and the chance depredations of insects! 

 etc. Measurements of growth must be made and growth is the 

 most important function of a young year, for the more it grows, 

 the larger will be the crops that it will be able to bear when 

 it comes to maturity. In experiments which are designed to 

 last only three or four years, the total increase in weight 

 of the tree may be determined ; for this purpose, as well as 

 to ensure uniformity, the trees are always weighed before 

 planting. When the experiment has to continue for a longer 

 time, other methods must be adopted. One of these is to 

 determine at intervals the general size of the trees by measur- 

 ing their height, the spread of the branches and the girth of 

 their stems. Another is to measure the total length of new 

 wood formed during the season, this being supplemented by 

 weighing the prunings. A third depends on determining the 

 relative size of the leaves : the sixth leaf from the end of each 

 shoot is removed and these leaves are dried and weighed. Occa- 

 sionally where the trees are small, the whole of the leaves are 

 removed and their weight determined. 



The results obtained by these various methods have been 

 compared with each other, as well as with determinations of 

 the dry matter and nitrogen in the leaves ; it is satisfactory 

 to find that they all show a substantial agreement : thus in each 

 of eight experiments eight different methods of measurement 

 were adopted and the order in which the experiment could 

 be arranged according to one of the methods was the same 

 as that obtaining in the case of the other seven, with only two 

 partial exceptions. Naturally, the actual magnitude of the 

 differences when measured by different features is not the 

 same, for some features will be more affected than others by 

 different treatment, e.g. the length of new wood formed varies 

 through greater limits than the size of the leaf. Where crops 

 have to be considered complication arises, for growth and 

 cropping are antagonistic to each other ; and such cases always 

 call for special discussion. 



