SEEDS AND SEEDLINGS 



groove on one side, leading from the small end to the big 

 end. Make a sketch of the side showing this line, label 

 it rhaphe, and the point where it begins, at the large end 

 of the seed, chalaza. Look for the hilum at the other 

 end of the rhaphe, and for the 

 micropyle near it, at the small 

 end of the seed. If they can 

 not be distinguished on account 

 of the lint, make a longitudinal 

 section of a well-soaked seed 

 and find where the hypocotyl 



209,210. Dissected cotton seed: pomts . Which wav did it 



209, seed with lint removed (magni- ^ . , ' . . 



fied three times). / funiculus, or point in the bean t 1 hlS IS the 

 seed stalk, r, rhaphe, ch. chalaza; casg w j th aU seeds the bage 



210, cross section of the seed still 



more highly magnified, showing the of the hypOCOtyl is towards 

 crumpled cotyledons. the micropyle) and so we can 



always tell where the micropyle is by noticing which way 

 the hypocotyl points. Make an enlarged sketch of the 

 section as it appears under the lens, and also of a cross 

 section of another soaked seed about midway between the 

 two ends, showing as accurately as you can the lines of 

 any folds or convolutions that you may see. Label such 

 parts as you can clearly make out, leaving the others till 

 after further examination. 



From a seed that has been boiled for five or ten minutes 

 to soften the contents, gently remove the coats so as to 

 leave the embryo whole. How many seed coats are 

 there ? How do they differ in color and 

 texture ? Try to distinguish them in 

 the sketches you have made, and label 

 the hard outer one that corresponds 

 to the shell of an egg, testa, the soft 2II ._ Embryo with 

 inner one, tegmen. What is the use of cotyledons partly un- 

 each ? As the coats were removed did folded - 

 they seem to adhere to the kernel more tenaciously at 

 one point than elsewhere? Look for a little dark spot 

 inside near the base, that marks where the seed coats and 

 kernel adhered together. Refer to your sketch of the out- 



