120 PLANT ANATOMY. 
starch granules, since the above-named transformation products 
possess the inclination, under suitable conditions, to again 
become deposited as solid starch (transitory starch). These 
small starch-granules, which are in process of migration, are 
thus found in the so-called starch-sheath, and in the sieve-tubes 
and medullary rays. They are also contained in some fruits 
before ripening (Olives, Fructus Conti, Fructus Juniperi, 
likewise the Fig). 
How the formation of starch is effected in the chlorophyll 
granules (assimilating-starch, p. 108) is, meanwhile, still an 
enigma. Only so much is certain, that for its production light 
is required,’ while potassium also appears to be indispensable 
for it.* 
The manner of circulation of starch may be elucidated by a 
single example. The species of Orchis which afford salep pos- 
sess, after the close of the period of vegetation, a tuber which is 
filled with starch and mucilage. The tuber is quiescent during 
the winter, and in spring develops a stem bearing the leaves and 
flowers. During the entire first period of development, the 
tuber provides the young shoot with nutritive material ; the 
starch migrates from the tuber upward into the shaft. In the 
course of further development, the leaves unfold, and now under- 
take on their own part the new formation of starch. But even 
now the plant provides for a future year. Beside the old, and 
now entirely exhausted tuber, a new rudimentary one is formed, 
into which the starch formed in the leaves migrates downward, 
in order to furnish the constructive material for the young plant 
during the next year. 
If the starch is dissolved in a reserve-receptacle, the gran- 
ules do not disappear at once, but solution gradually takes 
place, whereby a peculiar corrosion often occurs. Such corroded 
‘Compare Sachs, ‘“ Experimentalphysiologie der Pflanzen,” 1865; 
furthermore, Botan. Zeit., 1862 and 1864, ‘‘ Flora,” 1863, and researches 
of the Botanical Institute of Wirzburg, 1884.—Godlewski, Krakauer 
Akadem., 1875.—Béhm, Botan, Zeit., 1876, and others. 
? Proved by Nobbe in 1871. 
