THE STORAGE OF RESERVE MATERIALS 287 
along its axis. As the deposition proceeds the leucoplast 
becomes very much stretched longitudinally, till its centre 
is reduced to a thin film round the rod of starch, while 
what is left of its substance is accumulated at the two ends. 
The further activity of these portions results in the develop- 
ment of the two heads of the dumb-bell, the thin film 
connecting them ceasing to deposit any starch along the 
centre of the rod. 
| It is not very easy to 
\ see the leucoplasts in the 
potato; they can be de- 
fh yy tected, however, more easily 
at ir 
y \\ Hy 
— . 
Fia. 112.—Group or Rop-LikE 
Mi Levcopiasts, 2, EACH BEARING 
A Srarcu GRAIN, 8, COLLECTED 
Fig. 111. — Laticirerovs Cru ROUND THE NUCLEUS, n, OF A 
From Luphorbia, CONTAINING CELL OF THE PsEUDO-BULB OF 
Dumas - BELL- SHAPED STARCH AN Orcutp (Phajus grandifolius). 
Grains. x 500. (After Schimper.) 
in other plants. Fig. 112 shows a group of them forming 
starch grains in a cell in one of the orchids. The greater 
bulk of each lies on the outside of the grain; they are 
disc-like in shape and not round or ovoid as in the potato. 
In the temporary reservoirs which we have already 
noticed, such as pollen grains and tubes, the sheaths of 
cells in various regions of the stem, the tissue of the style of 
the lily, &c., the deposition of starch is not caused by leuco- 
plasts but by the general protoplasm of the cell. In these 
cases immense numbers of very small grains, hardly larger 
than mere specks, make their appearance, while the highest 
powers of the microscope fail to, enable an observer to detect 
