372. THE STRUCTURE OF ECONOMIC PLANTS 



eties, including the widely grown Bison, is produced in this coun- 

 try. For high quality fiber, most growers regard seed from the 

 Netherlands and Belgium, which has been derived from Russian 

 strains, as most desirable. 



GENERAL MORPHOLOGY 



The Root. — The root system consists of a slender tap root 3 or 

 4 feet in length with lateral branches that arise mainly from its 

 upper limits. Ten Eyck (14), in describing it, states that 



"flax has a different system of rooting from that of wheat or oats. 

 Its roots do not go so deep . . . but it makes a much greater fibrous 

 root growth in the upper two feet of the soil. Each plant sends down 

 a single, small taproot, which gives off many small side roots or 

 branches, and these in turn give off numerous fibrous roots or feeders. 

 The upper branches soon curve downward along with the main root 

 which grows rapidly slender and thread-like, until it can scarcely be 

 distinguished from its branches. ... By its intricate system of rooting 

 flax occupies the soil very completely." 



Arny and Johnson (3) studied the progressive development of the 

 Winona variety in Minnesota. They found that the tap root 

 reached a depth of approximately 3 feet, when the plants were 

 beginning to bloom and the stems were 2. feet tall, there being a 

 lateral spread of about a foot. The shallow main lateral roots grew 

 horizontally for about 6 inches, then turned sharply downward, 

 and ultimately equaled the main tap root in length. When the 

 plant was in full bloom, after nearly two months' growth, the tap 

 root was about 33^^ feet long; and another 6 inches was added in 

 the ensuing five weeks which brought it to full maturity. 



The Shoot. — The stem is slender and erect, branching at some 

 point above the middle, usually nearer the top, to form the few- 

 flowered inflorescence which may be a panicle, corymb, or cyme. 

 (Fig. 188.) In flax grown for fiber, the length of the stalk from the 

 soil surface to the lowest branches of the inflorescence is an im- 

 portant factor in determining quality, as only the unbranched 

 portion of the axis has commercial value since the fiber in the 

 branches is broken in the processes of fiber preparation. 



The simple leaves are linear to lanceolate, sessile, entire, and 

 without stipules. The leaf arrangement is variable, but the basal 

 leaves are commonly in alternate pairs, while those above the 



