1901 | BRIEFER ARTICLES 423 
A further examination showed that they grew in the greatest pro- 
fusion on the shelving side of the trunks of trees with a slant of 10° to 
20°; furthermore trunks which were nearly vertical were not inhabited 
by these minute plant forms. They were, however, nearly always found 
upon the slanting surfaces near the ground. In some cases the growth 
extended approximately to a height of 20 or 30 feet, and the position 
varied as the shelving varied, so that the eae might extend on the 
same tree at different heights from go° to 270 
Rather careful observations thus far obtained tend to show that it 
is the shelving portions of the trunks of trees which receive and hold 
the greatest amount of moisture, and as the latter is apparently one of 
the most important requisites for the development of these green 
plants, we can readily understand why we find them distributed on 
nearly all sides of the trees, and not limited, as popularly supposed, to 
the north side of trees only.— Henry Kraemer, Philadelphia, Pa. 
CONTRIBUTIONS TO THE KNOWLEDGE OF THE PHYSI- 
OLOGY OF KARYOKINESIS.' 
(WITH ONE FIGURE) 
THE investigations, concerning which this is a preliminary report, 
were undertaken to throw more light upon the subject of the physiol- 
ogy of karyokinesis, a subject which has not received attention com- 
mensurate with its importance. This paper presents only the results 
regarding the relationship of light of various wave-lengths to the rapid- 
ity of mitotic nuclear division. The investigations were undertaken 
at the suggestion of Dr. E. Mead Wilcox and were completed under 
his direction. I take this opportunity to offer him my sincere thanks 
for constant and helpful suggestions throughout the course of the 
investigations. 
The roots of Aliium Cepa were selected as affording the most con- 
venient and suitable objects for the experiments. Bulbs of uniform 
medium size were selected with great care in the local markets. These 
bulbs were placed over suitable vessels in such a position that the base 
of the bulb barely touched the pure water with which the vessels were 
filled. The usual adventitious roots soon formed, and these were 
* Contribution from the Botanical Laboratory of the Oklahoma Agricultural and 
Mechanical College. I. Abstract of thesis. 
