376 BOTANICAL GAZETTE [JUNE 
Coleus tricolor 
Four young and thrifty Coleus plants were put under compression 
in a similar manner as explained for Fuchsia. After a period of 
twelve days under a compression strain of 225%™, they were gathered 
and together with their controls were placed in 50 per cent. alcohol for 
examination later. 
Observations under a magnification of 150 diameters revealed no 
evidence of any differences between control and tension plants. We 
are hardly justified, then, in concluding that in these Coleus plants 
compression exerts any influence toward a development of mechanical 
tissue. For reasons that are apparent, the absolute amounts of 
xylem in both normal and tension plants were not determined by 
either the area or weight methods. The conclusion drawn was the 
result of detailed observations under the microscope by two persons 
working independently. 
é Conclusion 
The foregoing experiments were performed to determine the influ- 
ence of longitudinal compression upon the formation of mechanical 
tissue in the stems of Helianthus annuus, Vinca, Fuchsia, and Coleus. 
The results indicate that the stems of all the above-named plants 
except Coleus reacted to a compression strain by a self-regulatory 
development of mechanical tissue, yet the evidence cannot be called 
conclusive. 
C. INFLUENCE OF TENSION ON THE ROOT SYSTEM 
A number of papers on the influence of pull, or tension, on stems, 
petioles, and other aerial organs have been published, but nothing 
as yet has reached print concerning the influence of this treatment 
on the root system. It is the purpose of this section of the paper to 
‘ give the results of experiments along this line, and to show that in 
the root system we have an organ that reacts to tension by a self- 
regulatory development of mechanical tissue. 
Tension on the root system was applied by means of a pull upon 
the stem, brought about in the usual way by weights, when the 
seedlings had grown to a height of about 15°™ and the first pair of 
leaves had fully developed. 
The seeds for any one series of experiments on Helianthus annuus 
