68 
Beer. — On Elaioplasts. 
many of these cells scattered chloroplasts occur, arranged as in ordinary 
assimilating tissue (Fig. 15). These chloroplasts are large, and many of 
them contain droplets of an apparently oily nature embedded within their 
substance. Probably these oil-drops mark the first stage of degeneration, 
although the power of starch-formation has not yet been lost. I was at 
first inclined to believe that the oily drops within these chlorophyll cor- 
puscles represented the normal grana of these bodies developed to a rather 
unusual extent. The fact, however, that the chloroplasts of the other 
organs of Gaillardia (e. g., of the leaf) do not show any distinct grana of 
this kind, coupled with the further fact that the chlorophyll bodies of the 
pappus soon show undoubted signs of degeneration, has led me to conclude 
that the oil-drops are associated with the degradation of these chloroplasts. 
In other cells of the pappus-plates the chlorophyll corpuscles tend to 
hang, more or less loosely, together. In yet other cells the aggregation 
of the chloroplasts is closer, although the outlines of each separate plastid 
is still maintained (Fig. 16). A further step in this aggregation of the 
chlorophyll bodies is seen in other, neighbouring cells in which they 
become so closely clumped together that the outlines of the individual 
chloroplasts can no longer be distinguished, and we obtain a typical green 
elaioplast in which the oil-drops of the plastids produce the finely granular 
appearance characteristic of these structures. 
All these stages may be observed in adjoining cells of one and the 
same pappus-plate. They are best studied at about the time when the 
young pollen-grains are still without a membrane of their own and are 
enveloped in the special-wall (special mother-cell stage). 
In older pappus-plates the green colour of the elaioplasts gives place to 
yellow, and other degeneration processes become evident. 
Now that the development of the elaioplast has been followed in at 
least one species we are in a better position to compare this body with the 
oil-bodies of Hepaticae. Wakker evidently believed in the identity of the 
two structures, whilst other authors — such as Von Kiister ( 11 ) — held an 
opposite opinion. On comparing what has been written above regarding 
the elaioplasts of Gaillardia with Garjeanne’s careful account of the develop- 
ment of the oil-bodies of several Jungermanniales, it will be seen that the 
two structures have a very different origin. In the latter the oil-bodies 
arise as vacuoles in the cytoplasm, whilst we have seen that the elaioplasts 
of Gaillardia are formed by the aggregation of plastids and their degenera- 
tion products. Whilst, therefore, we cannot draw general conclusions until 
other species have been examined more fully, we may say that the develop- 
mental history of the elaioplasts of Gaillardia is essentially different from 
that of the oil-bodies of the Hepaticae. 
External conditions seem to exert very little influence on the 
appearance of the elaioplasts. 
