COMPARISON OF THE VARIOUS STRAWS BASED 

 UPON STRUCTURAL DIFFERENCES. 



External Gross Character. 



The four straws under examination may, if entire, 

 be readily distinguished by their stature, thickness, and 

 the shapes of the individual internodes and the minor 

 but nevertheless diagnostic characters offered by the 

 false nodes, by the shape of the upper part of the inter- 

 node just below the nodes, the sub-nodal constrictions, 

 and claws. The keys given below, as being the briefest 

 methods of description and at the same time most 

 easily usable, present the contrast of structure in 

 summary form. It will be understood that such keys 

 are useful only as descriptive of the four straws in- 

 cluded, and would require modification and extension 

 if other straws had to be considered (*). A possible qua- 

 lification might be forced even by races within the spe- 

 cies, and even by the age of the individual. Thus Car- 

 rier e.g. bases his classification of grain seedlings on 

 the presence or absence of claws, finding them present 



Figure 27. — Epidermis of wheat to show the crown cells. 

 The dwarf cells are also in evidence by the black outlines, 

 due to included air. The cells are somewhat separated from 

 each other by maceration, x 310. 



in all the grains but oat. It was difficult to find evid- 

 ence of claws in the sample of wheat straw supplied for 

 this work, but other samples showed them to be present, 

 but quite irregularly. Thus they may be present on one 

 side only, or totally absent, or, when present, they may 

 show much difference in size on the two sides of the leaf. 

 Rye, in common with wheat, betrays a considerable 

 amount of variation in this respect. 



The characters used in the keys are for the most part 

 such as may be detected readily even if the straw is 

 broken, and when the fragments are small. When 

 pulped however, identification must rest upon minute 

 anatomical characters which offer greater difficulties 

 of choice and application. Such characters are the 

 length of fibers, sizes of stomata, the presence or ab- 

 sence of triehomes ("comma cells," Weisner, 1865,) 

 characters of epidermal walls, and the like. 



Identification Keys Based Upon External Characters. 



Interior face of leaf sheath smooth; ligule long (ca. 

 4 mm.) ; claws absent; false nodes usually much shorter 

 than broad; terminal internode 2 or more mm. in dia- 

 meter near tip— oat. Interior face of leaf sheath rough, 



more or less, with upwardly directed short, stiff tri- 

 ehomes (comma cells) ; ligules short (1 mm.) Upper 

 part of terminal internode pubescent or hirsute, the in- 

 ternode tapering to slender dimensions (1 mm. dia- 

 meter) — rye. Upper part of terminal internode smooth 

 thick toward apex. Claws prominent, always present 

 — barley. Claws sometimes absent, small or various 

 in size — wheat. 



The dimensions of the false nodes when wet and dry 

 afford a means of identification of some value, though 

 more difficult of application. The following tables are 

 examples of such measurements. 



Measurements (diameter and length) of false nodes of 



barley, oat, rye and wheat in swollen condition, 



in millimeters. 





Basal 



Middle 





Top 





Diam. 



Length 



Diam. 



Length 



Diam 



. Length 



Barley 



5 



4.6 



3.5 



4 



4.8 

 4.5 



4 

 5.3 



4.2 

 3.7 



5.4 



7 



Oats 



5.5 

 4.6 



2.5 



2 



5.5 

 4.5 

 5.4 



2.6 



2.7- - 

 2.8 



5.3 



4 

 5 



3.2 

 2.6 

 3.5 



Rye 



4.5 

 4.5 

 5.2 



3 

 2.5 



3.8 



4.4 

 4.4 



5 



4 



4 

 4.7 



3.5 

 3.6 



4 



5.2 

 4.5 



4.5 



Wheat 







4 

 4.5 



2 

 3.5 



4 

 4.5 



4 

 3.8 



Measurements (diameter and length) of false nodes of 



barley, oat, rye and wheat, to the nearest 



half-millimeter, when dry. 





3rd 





2nd. 





Top 





Diam. 



Length 



Diam. 



Length 



Diam. 



Length 



Barley 



2.5 



3 



2.5 



4 



2 



1.5 





2.5 



2.5 



2.5 



3.5 



2 



4 









3.0 



3.5 



2.5 



4.5 





2.0 



2.5 



2 



3.5 



2 



4 









2 



3.5 



2 



4.5 



Oats 







4 



1.5 



3 



2 









4 



2 



3.5 



2 



V 







4 



2 



3.5 



2 









4 



2 



3 



2 









3.5 



2 



3 



3.5 



Rye 



3 



3.5 



3 



4 



2 



4 





3.5 



2.5 



3.5 



3 



2.5 



3.5 





3 



2 



\2.5 



3 



2 



3.5 





4 



3.5 



3.5 



4 



3 



4 





3.5 



3 



3 



3.5 



2.5 



4 



Wheat 







3.5 



3 



3 



3 









3.5 



2.5 



2.5 



3.5 









3 



2.5 



2.5 



3.5 









3 



2.5 



2 



3 









3 



3 



2.5 



3.5 



(*) See the bulletin by Lyman Carrier, 1917. 



COMPARATIVE ANATOMICAL CHARACTERS OF 

 STRAWS. 



Comparison of Distribution and Characters of Tissues 

 ae Seen in Sections. 



1. Transverse section of the terminal internode 

 (figures 16-19). There is little that can be regarded as 

 sufficiently characteristic in the structure as seen in 

 transverse section to serve as diagnostic. Of two 

 rather obvious points, that of size has already been 



