straw from the heads of sorghum (broom-corn) is used 

 in the manufacture of brooms and brushes. 



Tin; mechanical qualit ics which fix the value of the mat- 

 erial for these purposes are strength, lightness and 

 springiness which combined are exemplified in the 

 highest degree in the split bamboo fishing rod. Even 

 ordinary straw of common grains shows these qualities 

 in a remarkable degree, relatively to the amount of 

 material in it. One needs but to recall the lightness 

 and stiffness of a lemonade straw — now largely sup- 

 planted by imitation straws made of paper and paraf- 

 f ine — to realize this. 



The Structure of the Straw in General ; Gross External 

 Structure. 



As has been indicated, straw consists of two parts, 

 the stem and the attached leaves. The stem is composed 

 of straight stretches of approximately cylindrical shape 

 and varioxis lengths, the internodes, articulated at the 

 nodes. Properly speaking the node is merely the trans- 

 verse region of the stem from which arises a leaf. In 

 the grasses, however, the base of the leaf is usually 

 swollen, forming a prominent band (motile organ) about 

 the base of the succeeding internode (figure 1). In the 

 dried straw this swollen collar is shrunken, and pre- 

 sents characters which enables one to distinguish be- 





L-Cia 



a/ 



Leaf-sheaff? 

 /nternoc/e 



-Mottle organ 



Node 



internode 



tween the kinds of .straw here under consideration in 

 some degree. 



The leaf is composed of two parts, the leaf-sheath 

 and the blade. The leaf-sheath is the lower portion which 

 springs from the node and folds about the internode 

 above. At the top of the sheath the blade springs away 

 from the stem, and a1 this point is found a membranous 

 projection which clasps the stem apparently as a con- 

 tinuation of the sheath, known as the ligule (figure 1, 

 29).' The edges of the blade sometimes project, clasp- 

 ing the stem (figure 28). The projections are called 

 auricles or, more simply, claws. The size, shape and 

 other features of this organ serve as distinguishing marks 

 for identification, which, in the absence of the grain 

 and its accompanying parts, are relatively of great use 

 in the recognition of the kind of straw (Carrier, 1917). 



At the base of the blade there is always a more or less 

 conspicuous transverse zone, the collar, having, when 

 well developed, much the same structure as that found 

 in the swollen base of the leaf sheath, (as e.g. in orchard 

 grass). When inconspicuous, as is the case in the grain? 

 here to be considered, the collar is indicated only by a 

 more or less evident thickening of the veins as they 

 traverse it. The collar is a motile organ analogous to 

 the swollen leaf sheath base, and at this point the blade 

 bends into a position approximately at right angles to 

 the axis of the plant. 



The swollen leaf bases, which may here be called false 

 nodes for the lack of a better term, are important organs 

 by which the growing grass shoot maintains its upright 

 position. Should young grain be "lodged", the upper 

 portion of the stem will readily regain a vertical posi- 

 tion, and on examination it will be found that the re- 

 quisite bending has been confined wholly to the false 

 node and the ensheathed base of the included internode, 

 as evidenced by the unequal development of the false 

 node on the upper and lower sides. It is only rarely 

 that the lower parts of straw do not show more or less 

 bending. The false nodes and leaf sheaths, incidentally, 

 help to distribute the strains imparted to the straw by 

 bending, as e.g. under a heavy wind, so that the break- 

 ing of the stem at the base of an internode is usually 

 obviated. This view of the mechanics of the grass straw 

 has been denied, but without good reason. As a matter 

 of fact the younger tissues of the internode are at the 

 base, and the weight of the parts above could not be 

 successfully supported during development were it not 

 for the leaf- sheaths. This is very obvious in growing 

 corn (maize). In the dead, dry straws the false nodes 

 very obviously form supporting' bands, strengthening 

 the shaft at these points. To be sure the tissues are 

 in this condition hard and indurated, while in life they 

 are much softer and more pliable. In any event, how- 

 ever the mechanical value of the false node is but con- 

 tributory, while its primary function is that of a motile 

 organ, as above explained. 



The leaf in the grasses is always conspicuously ribbed 

 and veined, the veins running parallel, except for their 

 gradual convergence toward the apex, and the same is 

 true of the stem, except at the nodes, where the veins 

 branch and redistribute themselves into the leaf and 

 next node above (2). In harmony with the anatomical 

 scheme underlying the structure of grasses, there is an 

 evident elongation of most of the external and internal 

 structures. 



Fig. 1. — Longitudinal sections through a node of wheat 

 straw. The broken lines indicate the shape of the leaf base 

 (false node) when dry and shrunken. 



(2) This topic is apart from the present purpose, and 

 hence will not be further mentioned. Those interested 

 mav consult Chrysler, 1906. 



