232 The Philippine Journal of Science 1916 
The chief reason for this very considerable difference is not 
the rate of growth of active plants, but is rather the fact, that 
after the middle of the time of experiment there was a decided 
tendency for the plants in darkness to die at the tips. This was 
perhaps due to the dry atmosphere, perhaps to darkness itself. 
The death of the tip was usually followed by the appearance of 
branches. The plants in darkness had usually several axes, 
either by the branching of the shoot, or by the production of a 
number of successive shoots from the roof; while in light, the 
plants of most varieties produced a single shoot, which did not 
branch during the period of the experiment. What would ob- 
viously be expected, was true — the plants with one shoot reached 
a greater length than did equally thrifty plants with several 
shoots of which only one was measured. 
The possibility has just been suggested that the darkness is 
itself responsible for the blasting of the young tips and their 
replacement by branches. In the course of the experiment, it 
happened to nearly all of the plants, which were first to germinate 
and grow vigorously, that the vigorous shoots gradually grew less 
rapidly and presently ceased to grow altogether. This happened 
sooner in darkness, but eventually to many of the plants growing 
in light. My first impression in the case of the plants in light, 
which in several cases reached a length of nearly, or quite, two 
meters before growth ceased, was that the store of food was 
becoming exhausted or that the distance to which food might be 
transported from the root to support activity at the growing 
point had been reached or exceeded. However, it presently 
developed, that in every case of this kind one or more branches 
developed soon after the cessation of growth of the first tip and 
that at least one of these branches grew as actively as the main 
shoot had previously done and presently exceeded the main shoot 
in length. The experiment was continued long enough so that 
some of these branches in their turn ceased to grow in the same 
manner and were likewise outgrown by other branches. The 
total length from root to tip of branch was in a number of cases 
more than twice that of the main shoot. 
The plants in the laboratory, although spoken of as exposed 
to light, were not illuminated as plants are likely to be in nature. 
It occurs to me, that with anything less than normal illumination 
it may be natural for the tip of any one stem or branch to cease 
to grow after a time, unless it comes under conditions quite 
favorable to development as a permanent main axis of the plant. 
Under these conditions, the attempt is made next with a branch 
which at first, at least, follows a different course from the parent 
