THE STORAGE OF RESERVE MATERIALS 281 
the latter is an elongated structure, and at first forms a 
rod of starch 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 development 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 
wp if Pies = cant 
va \ ayy a A ‘ 
\ ae LAN Rl 
l Fic. 112.—GRoup OF ROD-LIKE 
Lervcorxasts, J, EACH BEARING 
( potato ; they can be detected, 
A STARCH GRAIN, $8, COLLECTED 
Fic. 111.--Laricirerous CELL ROUND THE NUCLEUS, 1, OF A 
From Euphorbia, CONTAINING CELL OF THE PSEUDO-BULB OF 
DUMB -BELL-SHAPED STARCH AN ORcHID (Phajus grandi- 
GRAINS. folius). x 500, (After Schimper.) 
however, more easily 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 
as in the potato. G 
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 
