86 



about Svdnev, contained that element, and this was the case with both C. rhom- 

 boidea and C. MitcUcri collected from this locality. The wood of cultivated trees of 

 Araiicaria Bidicilli, also growing upon the sandstone formation around Sydney, 

 contained manganese in fair amount, and it was also present in tlieir gummy 

 exudations. Although the manganese ma\- not be considered abundant in com- 

 parison with the other elements present, yet it evidently plays some important 

 part in the constructive processes of these plants — a result, the procedure of which 

 is at present little understood. 



Pfeffer, when dealing with the food of plants (" Physiology of Plants," 2nd 

 edition, p. 434, Ewart's Trans.), in speaking of the accumulation in plants of 

 non-essential ash constituents, says: — "Such accumulation is an example of 

 selective absorption, and is due to the fact that the substance absorbed is 

 converted into an insoluble form or into a non-diosmosing compound . 

 Similarly a plant may accumulate large quantities of poisonous bodies if they 

 are presented in such dilute forms that an injurious concentration is never 

 reached during the eudosmosis through the plasma. The poisonous metallic 

 salts are retained by humus with considerable tenacitv and presented to the 



plant in very dilute form Xe\'ertheless non-essential elements 



frequently become involved in metabolism, and are utilised to a certain extent 

 as is shown by their partial substitution for essential elements and by other facts. 

 Thus the non-essential elements, such as manganese, cobalt, or zinc may in certain 

 cases fa\'our growth .... just as calcium is necessary to most plants, but 

 not to all, so also ma\' silicon or similar elements be essential to a few plants only. 

 In a condition of nature, where the competition with other organisms is severe, 

 the trifling assistance afforded by a non-essential substance may be of decisive 

 importance." 



It is already becoming to be recognised from recent experiments that 

 minute traces of manganese do have a marked stimulating effect upon the growth 

 of certain plants. This has been shown by Uchiyama (" Bull. Cent. Exper. Stat.," 

 Japan, 1907); Gregoire, Hendrick, and Carpiaux ("Bull. Inst. Chim. Bact.," Gem- 

 bloux, 1908; ; Sutherst (" Transvaal .-\gric. Journ.," 1908) and others. It would now 

 be interesting to determine the real value of manganese in governing the rate of 

 growth of plants belonging to the Australian ConifercC, and the results thus obtained 

 would probably help considerably towards arriving at some conclusion as to the 

 real function of small quantities of those metallic salts, which in larger (juantities 

 seem to be detrimental to growth ; knowledge in this respect is at present \'ery 

 elementary, although a considerable amount of work has recently been under- 

 taken in this and corresponding directions. Bertrand "J. d'Agric. Pratique," 1906) 

 applied manganese sulphate at the rate of 50 kilos per hectare to land on which 

 wheat was sown, and obtained an increase in the total crop of 22.5 per cent. 

 Dr. Lankester {" Lectures on Food," London, 1861, p. 57) says that manganese 



