66 
Beer. —On Elaiop lasts . 
immature and entirely enclosed within the involucral bracts, no elaioplasts 
were yet to be seen. The cell contained a nucleus and cytoplasm which 
partly formed a peripheral layer and partly extended in strands and bars 
through the cell cavity (Figs, i and 2). Embedded in the cytoplasm was 
a number of small, highly refractive grains which had all the appearances of 
ordinary leucoplasts. That these refractive grains are really leucoplasts is 
confirmed by two facts. 
Firstly, the resemblance between the unquestionable, starch-forming 
leucoplasts occurring, for example, in the hairs which cover the very young 
leaves, and the highly refractive grains contained in the corolla-hairs, is 
complete, although starch is not found in the latter under the usual 
conditions of growth. 
Secondly, if the enveloping bracts be removed from a young in- 
florescence without detaching it from the parent plant, and the corolla-hairs 
exposed to a strong insolation, starch can be seen to have developed in 
some of these refractive grains. 
For these reasons I believe the highly refractive grains occurring in 
the cells of the corolla-hairs to be leucoplasts, some of which, however, may 
have lost the power of starch-formation. 
In somewhat older hairs these plastids, a number of which show signs 
of undergoing degeneration, tend to aggregate together at one or more 
spots within the cell. Not infrequently this aggregation of the plastids is 
in the neighbourhood of the nucleus, but in many instances it is found to 
occur at other regions of the cell (Figs. 3 and 4). 
At first the aggregation of the refractive grains is a very loose one, but 
it gradually grows closer and closer (Fig. 5) until the compact, highly 
refractive bodies are formed, which we have already recognized as elaio- 
plasts (Figs. 6, 7, and 8). The elaioplasts in the corolla-hairs of Gaillardia 
are, therefore, formed by the aggregation of plastids and their degeneration 
products at one or more spots in the cell. Within the elaioplast the plastids 
soon appear to undergo further degeneration with the production of an oily 
material. That Zimmermann should find a close similarity between the oil 
of the elaioplasts studied by him and the oil obtained from plastids is no 
longer surprising. 
All the plastids of the cell have not clumped together within the 
elaioplast. A certain proportion still remain scattered through the cell 
(Fig- 7)- 
For some time there is little alteration within the cell. The con- 
spicuous elaioplast may lie in almost any part of the cell, but often it takes 
up a position near the nucleus. In some instances it entirely envelops the 
nucleus, as I have represented in Fig. 8. 
In much older hairs we find the elaioplast undergoing a change. Its 
outline becomes less regular, and in some cases it becomes drawn out 
