594 



TRANSLOCAT10N 



seeds of the Leguminosae contain relatively too little non-nitrogenous 

 material, for asparagin accumulates to a marked extent in the seedling when 

 no photosynthetic production of organic (non-nitrogenous) substance is 

 possible. Moreover Godlewski 1 found that seedlings of RapJianus, ger- 

 minated in darkness or in air free from carbon dioxide, develop to a further 

 extent on an inorganic nutrient solution than they do on pure water. This 

 is because the seed is relatively deficient in ash constituents. In several 

 other seeds calcium is present in insufficient amount (Sect. 74). De Vries 

 found, however, that clover seeds contain the proper relative amount of ash 

 constituents 2 . Although certain plants are able to grow when supplied with 

 organic food solely in the form of proteids, it is usually the case that the 

 reserve-materials include both non-nitrogenous and nitrogenous substances, 

 and indeed the former are generally more abundant (Sect. 79). The com- 

 moner reserve-materials have already been mentioned, as also the fact that 

 no particular reserve-substance is essential for all plants. Starch, dextrose, 

 laevulose, fatty oil and cane-sugar are the commoner non-nitrogenous 

 reserve-materials, and they may either occur singly or several together in 

 the same plant. Inulin is less generally distributed, but often forms the 

 main reserve-substance in the underground parts of perennial Compositae. 

 Many other substances are restricted to certain groups of plants or are 

 localized in special organs ; thus glycogen is present in many fungi, while 

 reserve-cellulose occurs mainly in certain seeds (Sect. 83). Pectins and such 

 forms of carbohydrates as mannite, trehalose, gums or mucilage function as 

 reserve food-materials in a few plants (Sects. 82, 83), and organic acids 

 acquire a similar importance in the Crassulaceae (Sect. 85). Nitrogen is 

 usually stored in the form of proteids and amides, such as asparagin, leucin, 

 glutamin, &c. The proteids of seeds contain almost the whole of the 

 nitrogen present, whereas in tubers, bulbs, and rhizomes, frequently from 

 40 to 70 per cent, of the nitrogen occurs either in the form of amides, or of 

 other compounds, among which ammonium salts or nitrates are sometimes 

 especially abundant (Sect. 79). The ash constituents are deposited partly 

 as salts, and partly as organic compounds. Almost the whole of the 

 phosphorus, sulphur and iron is present in the seed in organic combination, 

 so that the reactions of the free ions are not given, whereas in bulbs, tubers, 

 &c., only a portion of these elements is retained in this form (Sect. 74). 



With the exception of reserve-cellulose the nutrient substances usually 

 accumulate within the living protoplast, and starch is actually imbedded in 

 the plasma, whereas fatty oils when abundant are excreted into the central 

 vacuole. The cell-sap also contains the greater part of the soluble food- 

 materials and the reserve-proteids, which when present in excess may 



1 Godlewski, Bot. Zeitung, 1879, P- 99- cf - also Pnuitl, ibid., 1881, p. 771 (Prothalli). 

 a De Vries, Landw. Jahrb., 1877, Bd. vi, p. 510. 



