1904] BILLINGS—TILLANDSIA USNEOIDES 113 
It was at once suspected that the various phases in distribution of the 
microchloroplasts were conditioned by the light intensity, and hence 
their movements could be made subject to control. Festoons of 
Tillandsia accordingly were placed under different conditions varying 
from darkness to direct sunlight. Those placed in darkness were 
allowed to remain there 24 to 30 hours, and a similar period of expo- 
sure was allotted to festoons hung in the shade. Those exposed to 
direct sunlight were hung up early in the morning. All were exam- 
ined during the hours between 11:30 A. M. and 3:00 P. M. 
The examination was made by sectioning numerous leaves of vari- 
ous ages, and from as many different regions of each festoon as pos- 
sible. Plants were also sectioned at different times of day and also at 
night. The results in every instance were approximately the same. 
Sections were obtained from plants under the varying conditions of 
light intensity used in the experiment; sections in which the mega- 
chloroplasts were present; in which they were in the process of disin- 
tegration into microchloroplasts; in which there was distribution of the 
microchloroplasts uniformly through the cell; and in which all the 
foregoing stages were present in the same section. In fact, the same 
leaf varied in these respects in its different portions. There seemed 
to be no method of telling before examination just what condition the 
chloroplasts would be in. One of the best instances of complete 
uniformity of distribution of the microchloroplasts throughout the 
cytoplasm was obtained from the tiny leaf of a seedling. That the 
disintegration of the mega- into microchloroplasts is not the result of 
injury due to sectioning may be proven by an examination of the entire 
leaf through the epidermis. Sections also cut thick contain in their 
centers cells untouched by the razor. 
Homogeneous chloroplasts of the usual type were found which 
showed evidence of undergoing division. Megachloroplasts, in which 
the microchloroplasts were distinctly visible, were also found showing 
a deep constriction as though they too were undergoing fission. 
Owing to the difficulty of observing well the interior of the leaf 
through the overlapping scales, it was not ascertained whether the 
microchloroplasts return to form megachloroplasts or not; but if so 
it seems certain that the latter would not be constructed of identically 
the same microchloroplasts a second time. 
