202 BOTANY 



but it must also be carried on in cells devoid of chlorophyll, as, for 

 instance, in those of the Fungi. 



As little is known concerning the process of the synthesis of the albuminous 

 substances of plants as concerning the formation of the carbohydrates from the 

 carbonic acid and water. It has generally been supposed that they are formed 

 from the carbohydrates and mineral substances already mentioned, as these are 

 known to be transported to the region where the formation of protoplasm occurs, 

 and are there consumed. The carbohydrates utilised in this process seem to he 

 principally glucose (both grape-sugar, dextrose, C 6 H 12 6 + H20, and fruit-sugar, 

 laevulose, C e H 12 6 ) and maltose- (C 6 H 22 O n + HoO) ; for, whatever may be the form 

 of the original carbohydrate, whether starch, inulin, cane-sugar, reserve-cellulose, 

 or glycogen, glucose or maltose is always the first product formed from it. 



The mineral nitrates, sulphates, and phosphates take part in the process, 

 chiefly in the form of potassium and magnesium salts. Nitrogen and 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 in 

 the cell nucleus. Calcium salts, although they take no direct part in these processes, 

 seem, nevertheless, to be indispensable. Their importance, indeed absolute necessity, 

 for most plants, is due to their functioning as a medium for conveying the mineral 

 acids, and for neutralising, or precipitating, injurious by-products which are produced 

 in the formation of albumen. The, most frequent of these by-products is oxalic acid 

 (C 2 H 2 4 ), which, either as a free ac'id or as a soluble potassium salt, acts as a poison 

 upon most plants. The oxalate of potassium, which is first formed from the potassium 

 nitrate, reacts with the calcium salts present, with the formation of calcium oxalate, 

 which is only slightly soluble and, as it accumulates, crystallises out and thus becomes 

 harmless. Wherever the formation of albumen or nuclein takes place, oxalic ac,id is 

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

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



The process of the formation of oxalic acid, or its potassium salt, might be con- 

 ceived of as taking place according to the following theoretical equation : 



C 6 H 12 6 +; 2N0 3 K = C 4 H 8 N 2 3 + K 2 C 2 4 + H 2 + SO 

 Glucose Potassium nitrate Asparagin Potassium oxalate Water Oxygen 



Starting with glucose and potassium nitrate, there would be formed in addition to 

 potassium oxalate, water, and oxygen (which for the most part is consumed in the 

 respiration, but also in many cases, as free oxygen, may be detected or estimated), 

 an amido compound, Aspakagin, C 2 H 3 (NH 2 ) (CONH 2 ) (COOH). Asparagin is a 

 body which, like oxalic acid, is widely distributed throughout the vegetable 

 kingdom. Particularly large accumulations of this substance (first discovered in 

 Asparagus) are found in etiolated seedlings of many Papilionaceae (1 litre of sap 

 from Bean seedlings contains about 12-15 grams), always, however, under circum- 

 stances which suggest the possibility that Asparagin participates in the synthesis 

 of the albuminous substances. In all probability its formation precedes that of the 

 ultimate proteid substances. Asparagin is soluble in water and watery sap, and so 

 is in a position to permeate the cell wall, which the colloid albuminous substances 

 are not able to do in the same degree. 



Transfer of the Products of Assimilation 



When proteid substances are to be conveyed through the tissues, 

 as, for example, from seeds rich in proteids into the seedlings, they 



