Vestibule short and narrow, rectangular (figure 



29a) barley 



Vestibule nearly as long as the guard cells 



(figure 29b) oat 



In studying the stomata in the inner epidermis of the 

 leaf sheath, it is necessary to observe the precaution 

 of excluding those, along the thin, papery margin, as 

 here they are narrow and hardly characteristic. 



In evaluating these measurements, too much weight - 

 must not be attached to the averages. The short and 

 slender fibers (6-10 microns in diameter) are reduced 

 in number — at least they are not to be readily found — ■ 

 in bleached pulp, so that the character of the pulp is 

 determined by the survival of the longer and the 

 thicker (10-30 microns) fibers. . 



Figures 34-35. — Fibers and other maceration products from 

 straw-pulp papers. Figure 34, oat; figure 35, wheat, x 20. 



The mechanical tissues (fibers). Figure 30-33). 



The mechanical tissues are made up of bast fibers 

 composed of single cells with thick walls, and gradu- 

 ally tapering toward either end. The ends of the fibers 

 are usually abruptly truncated by an oblique wall, 

 or may be very blunt or even bifurcated. 



There is little uniformity in length, as can be judged 

 by inspecting the figures herewith (figures 30-33), 

 and the thickness of the wall varies accordingly. 



Table of fiber length (in millimeters). 



Number of Stem Leaf sheath 



counts max. min. ave. max. min. ave. 



Barley .... 40 1.5 0.3 0.9 1.7 0.5 1.0 



Oat 110-40 4.6 0.6 1.8 1.9 0.5 1.2 



Rye 40 3.3 0.7 1.8 3.9 0.6 1.3 



Wheat .. .. 5--20 2.4 0.7 1.6 1.7 0.5 1.2 



In making the above measurements, certain long 

 cells found in the leaf sheath were purposely avoided. 

 These are the cells (some of which are marked 1, in 

 figure 25), which occur along the ventral (upper) 

 edge of the bundles and are especially long and thin 



walled, the walls with minute pores. Preparations were 

 made so as to include these fibers only, excluding as 

 far as possible the fibers from between the bundles 

 and the lower epidermis. The lengths of the longer 

 isolated cells (some are quite short) are: 



Barley about 1.7 mm. 



Oat 5 to 8 mm. 



Rye . . . about 4 mm. 



Wheat . 2 to 4.5 rnm. 



That is to say, these fibers, or rather fiber-like cells, 

 are roughly twice as long as the true fibers in barley. 

 and three times as long as in others, reaching the 

 greatest length in the oat. They are rather readily 

 found in paper pulp, forming but a small fraction of 

 the whole. 



An interesting and theoretically important question 

 always comes up in regard to fiber length and its 

 relation to position in the plant . Specifically stated, 

 it is to be expected that the long interno'des will 

 have longer fibers than shorter ones? or will taller 

 straw have longer fibers than shorter ones? 



Rye is the tallest straw. The average length of fiber 

 is little if at all greater than in wheat and oat. Meas- 

 urements of fiber length for the terminal internode in 

 rye, this internode being the longest, showed that the 

 longest fibers were about 1.4mm long, whereas in the 

 lowest basal internode they were 2.3mm long. There 

 seems therefore to be no direct relation between length 

 of straw and length of fiber. 



It is of course very difficult to apply fiber measure- 

 ments to pulped straw, since the working and the soft- 

 ening effect of the chemicals used result in bending 

 and twisting of the fibers (figures 34 and 35). For 

 critical determinations therefore, it is on the whole 

 advisable to depend on the characters afforded by the 

 epidermal cells. 



These, together with wood vessels (tracheids) and 

 parenchyma cells are always to be found in varying 

 numbers, and more or less distorted, according to the 

 length and character of the chemical treatment which 

 may have been used. But of all the elements, the 

 epidermal cells are the most resistant, and hold their 

 original characters the best on account of their thick 

 walls. 



Xylem, phloem, and associated cells; parenchyma. 



The impression is scarcely to be avoided that the 

 structure of the straws of the various grains is re- 

 markably uniform, a result to he expected from what 

 we know of the general homogeneity of the group 

 which they represent. This is especially true of the 

 tissues which we have not examined in detail for dif- 

 ferences, namely the tissues of the fibro-vascular 

 bundles and parenchyma. Only the most general state- 

 ments may be made with safety, and these do not lead 

 very far. For example, we may say that in general 

 the stature of the cells of all tissues' is in barley (fig- 

 ure 30) less than in the other grains, and we have 

 seen evidence of this in the measurements already 

 given. Beyond this, only extreme minuteae, such as 

 the shape and size of the pits in the wood (xylem ), 

 seem to offer any appreciable differences, and these 

 are of very uncertain value. It would seem that, from 

 the practical point of view, with the purpose in mind 

 of seizing on differences which can be made use of for 

 identification without too great difficulty, the features 

 which have been presented above will meet The need. 

 The Chaff, (Glumes and paleits.) 



In the preceding account there has been no attempt 

 to give any description of the chaff. This term is a 



