416 THE FUTURE OF ARID LANDS 
plantago (1) have indicated great promise of improvement by 
means of interspecific hybridization. 
Canaigre: An Example 
Recent experimental work with canaigre (Rumex hymenosepa- 
lus) by the Special Crops Project, Agricultural Research Service, 
Department of Agriculture, may be used to illustrate briefly some 
of the points mentioned. 
Canaigre, a distinctive species of Rumex, with tuberous, tan- 
nin-bearing roots, grows in scattered stands from west Texas to 
California and from Colorado and Utah to northern Mexico. In 
many locations the plants are not sufficiently concentrated to 
furnish roots for commercial exploitation. Furthermore, roots 
from plants in the extensive and accessible stands in eastern 
Arizona, New Mexico, and Texas are relatively low in tannin 
and difficult to extract. Any industrial use of canaigre for tannin 
will, therefore, necessarily depend upon roots from cultivated 
plants to maintain an adequate supply. 
Distinct variations in root, leaf, and seedstalk characteristics 
have been found in strains collected in various locations. Roots 
from different locations varied in tannin content from less than 
20 to more than 40% (dry weight basis). Similar wide variations 
between strains were found in non-tannin extractives which affect 
processing quality. When all the collections were grown under 
the same environmental conditions in southern Arizona, many 
distinctive characteristics were found to be heritable. 
The range of variation in the wild material is so great that 
practically every characteristic needed in a cultivated crop ap- 
pears to be available. Some selected lines consistently produce 
high yields of roots containing more than 35% of readily extract- 
able tannin. Other lines are characterized by desirable root shapes 
for mechanical harvesting, abundant seed production, and dis- 
ease resistance. It appears that through the use of appropriate 
breeding procedures, varieties can be produced that are distinctly 
superior to the wild types and productive enough for use as a 
cultivated crop. The use of F; hybrids for commercial production 
also appears to be a promising possibility. 
