RESEARCHES ON THE DEVELOPMENT OF STARCH-GRAINS, 805 
stems and petioles, and in the bundle-sheaths of their leaves. 
This starch, which is obviously not a product of assimilation, 
is produced by the leucophyll-corpuscles. Examples of this 
can be found in the Hyacinth (bundle-sheath), in the stem of 
Begonia cucullata (figs. 55, 56), and of Ozalis Ortgiesiz, in 
the cortex of the stem of Philodendron grandifolium. 
These leucophyll-corpuscles are very faintly tinged with 
yellow, if at all. They gave rise, to the cases observed, to 
starch-grains in their periphery, just like the chlorophyll- 
corpuscles which would have been produced there under or- 
dinary circumstances. In those cases in which the starch- 
grains have a definite structure, as in the stem of Begonia 
cucullata, they are excentric, and the more developed side 
is the one which is in contact with the leucophyll-corpuscle ; 
this naturally removes any doubt as to the physiological 
significance of the corpuscles. 
The question now arises as to whether or not the property 
of forming starch out of assimilated materials is peculiar to 
the leucophyll-corpuscles and to the starch-forming-cor- 
puscles, and is not possessed by the chlorophyll-corpuscles ; 
and, further, whether this property is lost when these cor- 
puscles become converted into chlorophyll-corpuscles. 
In order to obtain an answer to this question a root-stock 
of Tradescantia rubella was kept in the dark until the large 
starch-grains which were present in the mesophyll had 
entirely disappeared ;' it was then exposed for some time to 
light, which was sufficiently intense to effect the formation 
of normal chlorophyll-corpuscles, but not sufficiently intense 
to cause any formation of starch in consequence of assimila- 
tion.” The investigation of the axillary branches which 
were produced from it under these conditions (the apices of 
the branches were carefully removed before the commence- 
ment of the experiment) showed that there was no starch in 
the mesophyll, but that it was present in considerable 
quantity in the chlorophyll-corpuscles of the bundle-sheaths 
of the leaves and of the parenchyma of the stem. 
These observations are not, as might appear at first sight, 
by any means adverse to Sach’s theory, that the starch-grains 
found in chlorophyll-corpuscles are products of assimilation. 
On the contrary, they confirm this theory in certain points. 
The fact that the formation of starch in the mesophyll de- 
pends upon the same conditions as assimilation, whereas it 
' Sach’s method (‘ Exp. Phys.,’ p. 322) for the detection of very small 
quantities of starch was made use of. 
* That no assimilation took place was shown by the fact that the chlo- 
rophyll-corpuscles of the mesophyll produced no starch. 
