714 CHEMICAL PROCESSES IN THE PLANT, 



presented in a connected form in the section on the Transformation of Food-materials in 

 my Handbook of Experimental Physiology \ The reader will there find the reasons for 

 the views here given ; and a few examples will now be sufficient to render somewhat 

 clearer the general statements with regard to metastasis and the migration of the assim- 

 ilated substances. In the outset it must be stated that by grape-sugar or simply sugar 

 I understand a substance soluble in the cell-sap, easily reducing copper oxide, and 

 readily soluble in strong alcohol, although it may not always exactly correspond to the 

 grape-sugar of chemists, a point which is of but little importance for our present 

 purpose. 



I. The parenchyma of the bulb-scales of the Tulip — i.e. the four or five thick 

 colourless leaves which serve as reservoirs of reserve material — contains, as long as the 

 plant is dormant, in addition to considerable quantities of albuminous substances, a very 

 large quantity of coarse-grained starch. The presence of sugar cannot be determined 

 at this time by micro-chemical processes. As soon as the bud of the leaf- and flower- 

 stem which is concealed within the bulb, but which had already been formed with all 

 the parts of the flower during the previous summer, begins to elongate in February, 

 and roots make their appearance from the base of the bulb, small quantities of sugar 

 are found with the starch in the parenchyma of the bulb-scales. The whole of the 

 parenchyma and of the epidermis of the leafy stem, of the young foliage-leaves, of 

 the perianth, of the stamens, and of the carpels, becomes filled with fine-grained starch, 

 the substance of which has already been derived from the bulb-scales, where the starch- 

 grains have become transformed into sugar, which diff'uses into the growing organs, and 

 there, as far as it is not directly consumed, again supplies material for the formation of 

 starch-grains. 



Together with its consumption in the growth, at first slow, of the cell-walls, this 

 temporary re-formation of starch at the expense of that contained in the bulb-scales 

 continues at first in the young internodes, leaves, and flowers. The cells enlarge and 

 become continually more filled up with fine-grained starch till the time when the bud 

 comes above ground (Fig. 470). Then follows the rapid extension of the stem ; the 

 leaves expand, and the flower unfolds. With the considerable and rapid increase in 

 size of the cells accompanying this unfolding, the fine-grained starch disappears in all 

 these parts, sugar being temporarily produced which furnishes the material for the 

 growth of the cell-wall. When all the parts above ground are fully unfolded, the cells, 

 although much larger, are now devoid of starch. The corresponding loss which the 

 bulb-scales have experienced up to this time is clearly seen from the decrease of their 

 starch-grains ; they may be found in all stages of absorption. The turgescence of the 

 bulb-scales at the same time decreases, and they become wrinkled ; but the formation 

 of sugar in them still continues at the expense of the starch, even when the parts above 

 ground have already done growing. The starch stored up in the bulb-scales finds in 

 fact still another use ; while the flower-stalk is extending, the bud in the axil of the 

 uppermost bulb-scale begins to develope rapidly (it had already been formed in the 

 previous summer) ; its cataphyllary leaves swell and become filled with starch ; and 

 the residue of the starch not consumed in the growth of the flower-stalk is transported 

 from the scales of the mother-bulb through its base into the young bulb (Fig. 470, 2). 

 These scales become gradually entirely emptied of starch, and while the green foliage- 

 leaves exposed to light are assimilating and contributing their share to the growth of 

 the new bulb, they finally wither and dry up from the simultaneous loss of water and 

 of assimilated matters. The scales of the mother-bulb form thin brown membranes 



^ The researches of Schroder (Jahrb. fiir wiss. Bot. vol, VIL p. 261), Soraiier, Siewert, Roestell, 

 &c. (collected in Hoffmann and Peters' Annual Report on the Progress of Agricultural Chemistry 

 for 1868 and 1869, Berlin 1871) contain fresh confirmations of the account here given. [See also De 

 Vries, On the Germination and Growth of Seeds, Tubers, and Roots of cultivated Plants (Clover, 

 Potato, Beetroot) in Landwirthsch. Jahrbiicher, vols. 6-8, 1877-79.] 



