302 A, F. W. SCHIMPER. 
forming-corpuscles in the endosperm of Melandryum agrees 
in all important points with the mode of development of the 
chlorophyll-corpuscles of many leaves, and their development 
in the epidermis of Philodendron has its perfect analogue in 
the formation of chlorophyll-corpuscles in many stems 
(e.g. of Cereus speciosissimus!), and in the leaf of Vanilla 
planifolia.2. Again, the starch-forming-corpuscles, like the 
chlorophyll-corpuscles, produce starch-grains, although the 
origin of the grains is different in the two cases, inasmuch 
as in the latter they are the products of assimilation, whereas 
in the former they are formed from organic substances which 
had been assimilated elsewhere. 
A distinct analogy appears in the relation in space of the 
starch-grains to the point of their formation ; the same two 
types which we found in the chlorophyll-corpuscles recur in 
the starch-forming-corpuscles ; and, further, as has already 
been pointed out, the behaviour of the starch-forming-cor- 
puscles, after the formation of the starch-grains, is quite 
similar to that of the chlorephyll-corpuscles. 
But these relations may be extended much further. In 
most cases the starch-forming-corpuscles may be actually 
converted into chlorophyll-corpuscles under the influence of 
light. 
This conversion may take place normally and regularly in 
the development of a plant-organ; this is the case when the 
younger parts of the organ are protected from the light, 
either by a thick covering of leaves or by the soil, and are 
exposed to its influence at a later period (leaves of Iris, 
tubers of Phajus grandifolius). 
In organs which remain, as a rule, permanently in the 
dark, the conversion of starch-forming-corpuscles into 
chlorophyll-corpuscles takes place as soon as they are 
exposed to light; in this way the false chlorophyll-cor- 
puscles are produced which have been known, in the potato 
for instance, for so long. 
Certain parts of some organs are exposed to light, whereas 
others are more or less protected from it; this is the case, 
for instance, in stems, the bases of which are buried in the 
soil (e.g. Peperomia, Begonia, &c.), and in thick opaque 
organs of which only the external cells are affected by light 
(e.g. Philodendron grandifolium). In such cases all pos- 
sible intermediate stages between starch-forming-corpuscles 
and chlorophyll-corpuscles can be found. 
This conversion always takes place in the same way ; the 
? From my own observation. 
2 Gris, loc. cit., p. 188. 
