THE PRAIRIES OF THE PACIFIC NORTHWEST. 



37 



parts which pursue a downward course, or later extend out as laterals. Pri- 

 mary laterals are not much branched. The w^hole root from crown to near the 

 tip is covered with scattered small laterals, usually not over 2 mm. in diameter. 

 These are poorly branched, not often giving off roots of the fourth order. The 

 tip of the main root hkewise is Httle branched. The roots dry out and shrink 

 rapidly upon removal from the soil. The 18 plants examined had an average 

 root depth of 5 feet (fig. 7). 



Heuchera glabella. — This saxifrage has a strong tap-root supplied, especially 

 in the first foot of soil, with rather numerous but poorly branched laterals. 

 It reaches depths of about 5 feet (fig. 8). 



Leptotsenia miiltifida. — Leptotcenia is a subdominant which forms con- 

 spicuous societies in the vernal aspect. It has a large fleshy tap-root, some- 

 times 7 inches in circumference, wiiich may reach a depth of over 5 feet. The 

 fusiform roots may narrow down gradually or rather abruptly, even to a 

 diameter of 1 or 2 mm., and then again enlarge to a size equaling the original. 

 This is sometimes repeated several times, thus giving the root as a whole a 

 beaded appearance. In general the roots are very poorly branched. The 

 average depth of penetration is 5 feet (fig. 7) . 



HeliantheUa douglasil — This species, Hke the following, forms societies in 

 the autumnal aspect. It has a tap-root with a diameter seldom more than 2 

 cm. It throws out many large laterals just beneath the surface, most of 

 which come off within the first 18 inches of soil, although there are some 

 lower, and a cone may be formed aU the way to the tip. The laterals usually 

 pursue rather a vertically downward course and are profusely branched. Of 

 the 20 plants examined the deepest penetrated only to 5.5 feet, while the aver- 

 age depth was found to be 4.5 feet (fig. 8). 



Hoorebekia racemosa. — The strong tap-root of this plant sometimes reaches 

 a depth of 10 or 11 feet, but usually ends near the 5.5 foot level. The larger 

 laterals, if any, are often thro-^m off within the first 18 inches of soil. These 

 are branched to the third order and may run off in a rather horizontal direc- 

 tion. The tap grows directly downward and is sparingly branched aU the 

 wav to the tip. The main root is usually not more than 0.5 inch in diameter 

 (fig. 6). 



Lithospermiun ruderale. — The tap-root of this species varies from 3 to 10 

 inches in circumference and gives promise of a deeper root system than is 

 actually attained. Only one plant reached a depth of over 6 feet, while the 

 average depth of the 5 specimens examined was 4 feet 10 inches. Large 

 laterals were sent off from the main root at various depths from 1 to 2 feet. 

 These ran horizontally several feet before turning downward. 



Sieversia ciliata. — This species forms societies in the estiva! aspect. Few 

 roots of Sieversia penetrate beyond depths of 5 feet 6 inches. It sends out as 

 many as 20 to 30 roots from a single inch of its thick rootstock. None of these 

 roots is over 3 to 4 mm. in diameter. They pursue a vertically downward 

 course and branch profusely all the way to the tip, sending off laterals seldom 

 over 3 inches long but branched to the fifth order. The 11 plants examined 

 gave an average root depth of 4 feet 9 inches (fig. 7) . 



Sidalcea oregana. — This mallow is confined to north hillsides and low 

 ground. It has a tap-root which gives off strong laterals, beginning in the 

 first foot of soil. The tap penetrates to depths of only 3 or 4 feet. The roots 

 are characterized by the origin of short laterals in groups of 3 to 8 (fig. 8) . 



