88 



SEEDS AND SEEDLING'S 



remove the plumule with the hypocotyl from the cotyle- 

 don, and sketch it. Make a vertical section of another 

 soaked grain at right angles to its broader face, and sketch 

 it, labeling the parts as they appear in profile. Make a 

 cross section through the middle of another grain, and 

 sketch it. (A very sharp instrument must be used in 

 making sections, or they will not be satisfactory.) 

 What proportion of the grain is endosperm and what 

 embryo .'' 



It has been seen that one of the effects of iodine is to 

 turn starch blue, or even black (Sec. 26). Put a drop on 

 some of the endosperm and note the 

 effect. Of what does it consist ? 

 Test the seed coats in the same way 

 to see if they contain any starch. 



119. Study of a Typical Small 

 Grain. — - Make a similar examination 

 of a grain of oatS or wheat. Compare 

 the endosperm of a soaked grain with 

 that of an unsoaked one; what change 

 has taken place and how do you 

 account for it ? Test with iodine and 

 see what it consists of. Which con- 

 tains the greater proportion of endo- 

 sperm, wheat (or oats) or corn ? 

 Notice that both the kinds of grain just examined have but 

 one cotyledon, hence, such seeds are said to be tnono- 

 cotyledonoiis. The grains are not typical seeds (Sec. 91), 

 but are selected for examination because they are large 

 and easy to obtain, and germinate readily. Other mono- 

 cotyledonous seeds should be examined if practicable. 

 The blackberry lily {Belamcanda) and iris furnish good 

 examples. 



200, 201. — Dissection of 

 a grain of oats : 200, entire, 

 and slightly enlarged, 

 showing c, cotyledon, p, 

 plumule, A, hypocotyl; 201, 

 vertical section, c, coty- 

 ledon, e, endosperm, /, 

 plumule, h, hypocotyl. 



120. Polycotyledons. — Remove one of the scales from 

 a pine..cone and sketch the seed as it lies in its place on 

 the cone scale. The seed with its wing looks very much 



