ASSIMILATION AND METASTASIS. 



637 



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. 441). 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 caused by 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 de- 

 crease 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 ex- 

 tending, the bud in the axil of the upper- 

 most bud-scale begins to develop rapidly 

 (it had already been formed in the previ- 

 ous 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. 441,2). 

 These scales become gradually entirely 

 emptied of starch, and while the green 

 foliage-leaves exposed to light are assimi- 

 lating 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 reserve-materials which accumulate 

 in the daughter-bulbs are partly derived 

 from those of the mother-bulb ; but are 

 completed by the products of assimilation 

 of the green leaves of the flower-stalk. 

 When the flower-stalk has also died down, 

 nothing remains of the whole plant but the 

 bud which has developed into a new bulb. 

 For a time it does not put out any new 

 organs, but is apparently dormant ; but in 



the interior the end of the stem continues to grow slowly, and produces new rudi- 

 ments of leaves and the flower-bud for the next year ; when the process now described 

 is repeated. 



So far we have only pointed out the relation of the starch and of the sugar 

 produced from it to the growth of the plant ; there are formed however along with 

 it, and probably likewise at the expense of these carbo-hydrates, other substances, 

 such as the colouring matter of flowers, the oil in the pollen-grains &c. The albuminoids 

 at first contained in the bulb-scales become transported to a distance from them. 



Fig. 441-— Longitudinal section through a germinating 

 bulb of Tulipapyacox: h the brown enveloping membrane, 

 k the flattened stem which forms the base of the bulb and 

 bears the bulb-scales sh ; si the elongated part of the stem 

 which bears the foliage-leaves ^'/', and terminates in the 

 flower; c the ovary,/ perianth, a anthers; 2 a lateral bulb 

 in the axil of theyoungesf bud-scale, which developes into 

 the bud of next year's bulb ; -w the roots which spring from 

 the fibro-vascular bundles of the base of the bulb. 



