CELL-CONTENTS AND CELL-WALLS. 65 



(6) In the embryo (compare transverse and longitudinal 

 sections of the grain) note (1) the scutellum, abutting on 

 the endosperm and consisting chiefly of small cells but 

 showing on the surface a very distinct epithelium layer 

 of narrow vertically elongated cells ; (2) at the upper end 

 of the embryo, the growing point of the shoot, covered by 

 the young foliage-leaves and enveloped by the plumule- 

 sheath ; (3) the radicle, showing very regular longitudinal 

 rows of cells, with the distinct root-cap covering the grow- 

 ing-point, and the radicle-sheath surrounding the whole 

 root ; (4) the vascular bundles seen at the junction of 

 scutellum, plumule, and radicle, with veins diverging into 

 these three organs ; (5) a small appendage epiblast 

 opposite the scutellum at the junction of the plumule and 

 radicle sheaths; (6) the spiral and annular vessels of the 

 bundle which enters the base of the grain look for these 

 in both longitudinal and transverse sections ; (7) the fine 

 tapering hairs at the apex of the grain. 



(c) Test sections for starch, sugar, and proteids ; there 

 is no sugar in the dry resting Wheat grain ; the embryo 

 contains proteins, but no starch ; the endosperm contains 

 both starch and proteins. 



(d}* Examine Wheat seedlings from time to time, and 

 test sections for starch, sugar, and proteins. At an early 

 stage sugar appears in the endosperm ; soon afterwards 

 transitory starch grains appear in the scutellum (except 

 the epithelium), and starch is also detected in the cells of 

 the elongating plumule-sheath and of the young growing 

 leaves within it. 



(e) Squeeze out the milky contents of germinating 

 Wheat grains on a slide, and note the corroded starch 

 grains. Also squeeze some germinating grains into a 

 test-tube, shake with water, and filter ; test the filtrate for 

 sugar with Fehling's solution. 



76. Inulin. This carbohydrate is found as a reserve 

 substance in many plants. It is soluble, but not readily, 

 in cold water, though it occurs in the cell- sap in solution, 

 p. B. 5 



