GERMINATION, GROWTH, TISSUE TENSION. 141 



posite side, and the patch of hairs at the other end ; 

 remove the embryo from the endosperm, to see the small 

 rounded convex scutellum ; cut transverse and longitudinal 

 sections, and treat with iodine. 



180. Maize and Wheat Seedlings. Wheat germin- 

 ates more readily than Maize, but seedlings of both should 

 be examined. 



(a) Note that the husk breaks open at the embryo end 

 of the grain, the radicle growing out first but not giving 

 rise to the whole root-system of the plant (as normally 

 occurs in the Bean, for instance), and later roots arising 

 from the hypocotyl region of the embryo, i.e. from the base 

 of the plumule. 



(6) Note that all the primary roots agree with the 

 radicle itself in bursting from a sheath which remains as a 

 collar at the base of the root ; this is especially well seen 

 in Wheat, where a first and a second pair of roots, right 

 and left, succeed the radicle, then a fifth root these five 

 roots can all be recognised in the resting grain (examine 

 series of transverse as well as longitudinal sections of grain). 



(c) Note the tubular sheath through the burst apex of 

 which the first foliage-leaf makes its appearance. Com- 

 pare this with earlier stages of germination, noting that 

 the sheath is at first closed at the top but is burst by the 

 rapidly elongating foliage-leaf after the tip of the cone is 

 carried well up into the air. 



(d) Make a longitudinal section of the grain and of the 

 young shoot, and note that the endosperm, especially near 

 the young plant itself, is reduced to a pulp ; the cotyledon 

 remains in its original position and acts as a digesting 

 and absorbing organ. In Wheat the grain soon becomes 

 shrunken and the endosperm reduced to a milky fluid ; in 

 both seedlings examine some of the endosperm and note 

 that the starch grains are being corroded and broken up 

 under the action of diastase. Remove the pulpy endo- 

 sperm from a seedling, and note the shape of the convex 

 shield- like cotyledon oval in outline in Maize, circular in 

 Wheat. 



