Gross Internal Structure. 



In most grasses the stem, excepting at the nodes, is a 

 hollow cylinder of almost geometrical regularity. The 

 exceptions in which the stem is a solid mass of tissue 

 are, conspicuously, the sugar cane, Indian corn and a 

 few others. The hollow joints of bamboo, used as flower 

 holders, and in the tropics as water holders, flowerpots, 

 etc., are familiar examples of the hollow structure ; still 

 more so the lemonade straw. 



As a mechanism possessing the maximum strength 

 relatively to a minimum amount of material it ap- 

 proaches perfection, that characterizing the hollow 

 column. Owing to the properties of the materials, 

 which have a high modulus of bending, the column is 

 not easily broken even under a transverse strain. The 

 terminal internodes of the rye serves as an excellent 

 example. One 55 cm. long, 0.7 mm. in diameter at the 

 upper end, and 1.2 mm. at the thickest point and weigh- 

 ing only 0.25 grams could support 5 grams when sup- 

 ported 10 cm. from the base, with bending through an 

 arc of 15 degrees in the dry condition. The walls of 

 the cylinder were only 0.2 mm. thick. It is of course 

 only when the strength available comes within the ord- 

 inary range of necessity that grass stems become useful 

 for the inherent mechanical properties, the bamboos 

 being in this regard notably efficient. Even grain 

 straws however, meet special needs, but aside from ord- 

 inary experience. 



Each internode tapers slightly towards the base, and 

 is generally somewhat constricted just below the node. 

 The terminal internode however tapers gradually, from 

 its thickest part, which is nearer the base, to the ear (in- 

 florescence) . The entire upright stem, or straw, con- 

 sists of three to four internodes in barley, oats and rye," 

 in wheat three, excluding the shorter internodes which 

 occur within 6 inches of the ground. The differences 

 in the length of straw are due chiefly to differences in 

 the length of the internodes, and less to their numbers. 

 The relative lengths and total lengths, based on the 

 measurement of ten straws of each grain are shown in 

 the table, (figure 2.) 



TABLE. 



Species Total length Length of internodes 



of straw Top 2 3 4 5 



cm. cm. cm. cm. cm. cm. 



Barlev 56 28 17 8 3 



Oat 91 49 24 16 2 



Eve . . . .• . . 149 53 46 28 12 10 



Wheat 69 42 22 5 . . 



The measurements for the bottom internodes in the 

 above samples are however only partial, since in reap- 

 ing, a basal portion of the straw is left. Measurements 

 of complete straws based on samples grown at MacDon- 

 ald College, and at Ottawa, in pure, or nearly pure 

 cultures, gave the following measurements : 



Barley — 



" Chevalier " . 



Oats— 

 "50 lb. Black" 

 "Banner" . . 

 "Alaska, 712" 

 "Banner" . . 



Total Top 2 3 4 5 6 7 



. 79 26 19 12 10 6 3 3 



103 34 24 17 14 10 4 . . 



. 81 41 17 11 7 4 1.. 



. 84 41 17 13 8 4 1.. 



. 95 41 22 15 9 6 2.. 



. 98 42 20 15 10 7 4 .. 



42 



32 



21 



13 



6 



2 



39 



32 



20 



13 



6 



2 



50 



21 



11 



8 



4 





52 



21 



11 



7 



2 





58 



23 



12 



8 



4 





50 



17 



9 



6 



2 





Rye- 

 Common Ill 



112 



Wheat— 



"Marquis" .... 104 

 "Marquis" .... 93 

 "Red Fife" . . . 105 

 "Pringles's Champ" 84 



It is evident that, due to both racial characters and 

 to "place effect" it would, not be easy to identify the 

 grains merely by casual measurements of the straws. 

 Nevertheless certain features emerge from the above 

 figures which serve as a guide of some value, espe- 

 cially in the relative lengths of the uppermost inter- 

 nodes. For example, the terminal internode in wheat 

 is 50 per cent, of the whole straw in length, and over 

 twice that of the sub-terminal internode. Similar com- 

 parisons bring out equally useful ratios, but it is un- 

 necessary here to discuss them further. We may say 

 however that it would be possible, given the samples of 

 straw, to fix upon the grain with fair certainty by such 

 measurements as these alone, and in conjunction with 

 other measurements, to arrive at practical certainty. 



We note that wheat has one less internode in the 

 straw than the others. About one in ten rve straws 



Figure 2. — Sector of a transverse section of a wheat stem 

 taken just above a node, where the fistula is not developed, 

 and the stem therefore solid. X 65. 



Figure 3. — Transverse section through an internode of bar- 

 ley, showing the fistula, and the bundles in the parenchyma. 

 X 6.8. 



Figure 4. — Sector of a transverse section through the 

 upper part of the terminal internode of wheat. The fiber 

 layer is interrupted by the chlorenehyma spaces (Chi which 

 underlay the stomatal zones in the epidermis. X 97. 



Figure 5. — A longitudinal section of the stem of barley. 

 The fiber layer (zf) appears quite dark on account of the 

 small diameters of the cell lumina. The ring and spiral 

 thickenings of the wood of two bundles (x) can be well seen. 

 A secondary series of wood vessels can be seen on the right 

 of the annular vessels of the left hand bundle. X 65. pa. 

 parenchyma; f. fibers. 



