-2-1-1 1JOTANV PAKT I 



Tlie mineral nitrates, sulphates, and phosphates t.-ike part in the process, chiefly 

 in the form of potassium and magnesium salts. Nitrogen anil sulphur are liberated 

 from the nitrates and sulphates, with decomposition of the acid radicals ; while of 

 the phosphates, the acid group is utilised in the formation of nuclein. Iron, which 

 is an essential for all plants whether or not they contain chlorophyll, appears to 

 enter into the composition of the nut-rein. According to recent experiments 

 calcium salts appear to play a more immediate part in the p rote id synthesis than 

 was formerly supposed to be the case. Their importance, for most plants, is due to 

 their functioning as a medium for conveying the mineral acids, and for neutralising 

 or precipitating oxalic acid (C.,HoO 4 ). The oxalate of potassium, which is lirst 

 fiirmi-d from tin- potassium nitrate, reacts with tin- calcium salts present, witli the 

 formation of calcium oxalate, which is only slightly soluble, and crystallises out as 

 it accumulates. Wherever the formation of albumen or nuclein takes place, oxalic 

 acid is formed, the calcium salts of which may usually be found in adjacent cells, 

 in the form of aggregates of crystals, raphides, or crystal sand. 



On account of their occurrence and behaviour in plants, the amides and hexa- 

 carbon bases are regarded as preliminary stages in the formation of albuminous 

 substances. Among the amides ASPAIIAGIX, CoH :J (NH 2 )(CONHo)(COOH), is note- 

 worthy on account of its wide distribution. It is present in abundance in Gramineae 

 and Leguminosae (one litre of sap from Bean seedlings contains about 12- 15 grammes). 

 In the Cruciferae and Cucurbitaceae it is "replaced by glutamin, while in the 

 Coniferae a hexa-carbon base (arginin, C B Hi 4 N 4 2 ) appears to play the same role. 

 Any real knowledge of the mode of origin and transformation into more complicated 

 albuminous compounds of these and similar nitrogenous substances (c.ij. betain, 

 leucin, tyrosiu, and allantoin) is at present wanting. 



The colloidal nature of many albuminous substances, which hinders their 

 osmotic diffusion, is of importance since it facilitates their recognition by appro- 

 priate reactions and their localisation in the protoplasm ( 42 ). 



Transfer of the Products of Assimilation 



AVhen colloidal proteid substances are to be conveyed through the 

 tissues, as, for example, from seeds rich in proteicls into the seedlings, 

 they are first by a hydrolytic process decomposed into soluble sub- 

 stances. According to SCHULZE ( 43 ), albumoses and peptone are first 

 formed, and these are then broken up into amides and hexa-carbon 

 bases, and sometimes even into compounds of ammonia. They are in 

 this diffusible form transferred to places where, in combination with 

 carbohydrates and mineral acids, they are used anew along with 

 carbohydrates and salts in the formation of albumen. 



In addition to the transfer of nitrogenous constructive material 

 through the parenchymatous tissues, the LONG-DISTANCE TRANSPORT 



OF THE READY-FORMED ALBUMINOUS SUBSTANCES seems to take place 



through the open sieve-tubes of the bast. It appears to be in the 

 sieve-tubes, which contain, during life, albuminous substances, starch 

 grains, drops of oil and leptomin, that the conduction of organic 

 substances is effected from the leaves. The increased thickening of 

 the cortical layers observed just above wounds made by ringing trees, 



