GRASSES OF IOWA. 



SI 



a delicate formition consisting 

 of parenchyma withou , fibro- vas- 

 cular bundles, and its morpho- 

 logical nature is still doubtful. 

 Yet the view that it is the rudi- 

 ment try second cotyledoa is the 

 most reason -ible, for among o her 

 things this makes comprehensi- 

 ble the surprising position of the 

 first leaf of the plumule of the 

 embryo, consisting of a very 

 short, often indistinct internode 

 of the axis (epicotyl), and of two 

 to four leaves, and according to 

 the development of the former 

 the plumule is sessile or petioled. 

 The first leaf, the germ-sheath, 

 surrounds the others like a closed 

 tube, which breaks through the 

 ground with its hard point at the 

 time of germination, and opens- 

 at its apex after a time to allow 

 the exit of the second leaf. It is 

 colorless or pale green or fre- 

 quently reddish. Many authors 

 consider it a part of the cotyle- 

 don, a view which is certainly in- 

 correct, for in many grasses it is 

 separated from the scutellum at 

 the time of germination by a distinct internode, which is often 

 much elongated. In others this epicotyl is very short or 

 entirely lacking, so that the back of the sheath may even be 

 grown to the scutellum. 



" The majority of grasses have only one radicle, and grow 

 therefore with a primary root; in addition to which, especially 

 from the epicotyl, new roots soon arise which finally exceed 

 the main root in growth. In several grasses, especially in the 

 cereals, and also in Coix lachryma and other.-, the foundation 

 of these secondary roots is already laid before germination, 

 usually in the hypocotyl (the axis below Ihe insertion of the 

 scutellum); seldom and only to a rudimentary degree, in the 

 epicotyl. The planes of these secondary roots are parallel to 

 6 



Fig. 53. Squirrel-tail grass germi- 

 nating, sterile spikelets, young plant 

 and roots. (King.) 



