260 



CASSELL'S POPULAR GARDENING. 



important element of plant-food, along with abun- 

 dance of all the others, the amount of increase which 

 it yields will obviously be measured not by those 

 constituents which are abundant, but by that which 

 is deficient. 



By the courtesy of Professor Jamieson we are able 

 to place before our readers some interesting experi- 

 ments bearing upon this part of our inquiry. Having 

 obtained some pure white sand, from which all im- 

 purities had been removed, about 6 lbs. was taken, 

 and mixed with all the chemical substances or 

 ingredients considered essential to plant-growth, in 

 about the proportions in which they would exist in 

 Turnips. The mixture (sand and manure) was then 

 placed in a funnel-shaped vessel leading into a large 

 bottle (Fig. 8), and several Turnip-seeds were sown 



A 



Fig. 9.— Turnip Plants grown with 



the other ingredients were present in 

 abundance, the healthy seed produced 

 vigorous young seedlings, but speedily 

 the whole of them died. 



In vessel c, calciima and all the 

 other ingTcdients were supplied, but 

 phosphoric acid was omitted. The 

 result was identically the same as in 

 vessel B : the plants brairded well, but 

 soon died. 



In vessel d, where the Tuinip 

 showed a small growth, the conditions 

 were the same as in a, but potash was 



omitted. However, owing to some Fig. 8, 

 small specks of mica in the sand, which 

 could not easily be separated, the plant seemed to get 



AND WITHOUT VARIOUS FOOD ELEMENTS. 



m it, which were watered occasionally with water 

 purified for the purpose. In due time the Turnips 

 brairded. After some days they were thinned, 

 leaving only the central or healthiest plant. The 

 results of the various experiments are shown in Fig. 9. 

 In vessel a the growth went steadily on ; a luxuriant 

 mass of leaves were formed, and eventually a bulb 

 commenced and continued to develop till it was 

 taken up for illustration. The Turnip in vessel b 

 was so small that it appears almost as a mere speck 

 on the paper. Whence is the difference ? Precisely 

 the same sand, the same seed, the same watering, 

 and precisely the same ingredients added, save one, 

 which was purposely omitted— namely, calcium, or 

 lime. In consequence of this omission, although all 



from it just as much potash as enabled it to live. The 

 presence of mica would seem to imply that this 

 mineral is fitted materially to promote the fertility 

 of a soil in which the other earthy ingredients are 

 properly adjusted. Hence, a developed plant con- 

 tinuing in life, but miserably dwarfed. 



With Turnip e the peculiarity was the absence in 

 the manure of nitrogen. Unlike d, there was none 

 in the sand, and there was none supplied. True, it 

 was surrounded by abundance of nitrogen in the air ; 

 but we have previously seen that plants cannot assi- 

 milate the free nitrogen of the atmosphere ; but it is 

 thought there was a slight absorption through the 

 sand by the roots. However obtained, it confirms 

 Turnip D, viz., any important ingredient in small 



