378 BOTANICAL GAZETTE [JUNE 
gradually, and attained greater length; the lateral roots were gener- 
ally more numerous, larger in cross-section, straighter, and longer. 
The greatest growth of lateral roots was always found at the crown 
of the main root near the surface of the ground. 
Helianthus annuus 
To show the differences in root form between the normal and 
tension plants, two series of experiments were made on Helianthus 
annuus. The results of both were in general the same. All plants 
compared were of the same size and were grown in the open field 
under similar conditions. The first series was under experiment 
from July 8 to July 21, the second from September 21 to October to. 
The final weights to which the plants were subjected varied from 
750 to 1o008™, 
The following are observations obtained from a comparison of 
the root systems of two seedlings of the same relative size and vigor. 
These were representative seedlings and the results obtained were 
characteristic of the entire set of thirty-four plants: The main root 
of the tension plant was straight for a distance of 6°™, that of the 
control plant undulate throughout its whole course. The main roots 
had the same diameter at the upper ends. At 5™ below the first 
lateral root, the diameter of the tension plant was 3™™; while that of 
the normal plant was 2™™. The normal plant had a cluster of 10 
lateral roots at the upper end with a diameter of 1™™ or more; while 
the tension plant had at its upper end a cluster of 13 lateral roots 
with a diameter of 1™™ or more. All ‘these were longer, much more 
branched, and in general appearance stronger than the lateral roots 
in the normal plant. 
Here the differences between normal and tension plants were 
very marked, and it will be noticed later that marked differences 
appear as a result of microscopic observations. 
Ricinus communis 
The same general differences in external root form are noticeable 
in Ricinus communis. With this, as with the sunflower, two serles 
of experiments were run through. The first was under experimenta- 
tion from July 5 to July 21, and the second from September 26 to 
