STUDIES OF SEED-PLANTS 147 



various stages grown on moist paper ( 81), which may be preserved 

 for years in 5 per cent formalin solution; some peas planted one 

 week, and some two weeks before the lesson, some in soil in pots and 

 some in a tumbler or lamp-chimney arranged as described in 81 ; 

 and some seedlings with hypocotyl marked with waterproof ink to 

 determine the region of most rapid growth (see Fig. 34, bean). 



In connection with this lesson on seeds consult figures in Atkinson's 

 "First Studies of Plant Life." 



Examine pea seeds, following the directions given for the bean 

 ( 79). Examine seedlings of various stages and compare with those 

 of the bean. Especially compare the ways of the two plants in 

 getting out of the soil. Make sketches showing structure of the 

 pea seed and stages in its germination. Write in your note-book a 

 short paragraph comparing the germination of pea with bean seeds. 



Recall that the stem part of. the hypocotyl (that is, the stem 

 between root and cotyledons) elongated rapidly during germination 

 of bean seeds and pushed the cotyledons out of the soil (consult 

 your labeled drawings) ; and then try to explain why the cotyledons 

 of the pea seed remain where they are planted in the ground. Ex- 

 amine specimens of pea seedlings whose hypocotyls have been 

 marked with waterproof ink (see Fig. 34, 81), and determine whether 

 the root has been growing downward, or the stem just below the 

 cotyledons elongating rapidly, or both. Make sketches and compare 

 with corresponding sketches of marked bean seedlings. 



137. Squash Seed. (L) Materials : dry squash seeds ; seeds 

 soaked in warm water for 12 hours ; seeds soaked for 24 hours ; seeds 

 in various stages of germination (may be preserved in formalin) ; 

 seeds planted in soil two or three weeks in advance of lesson ; and 

 also seeds placed in various positions in a lamp-chimney or tumbler 

 as in 81, so that the students can follow the changes from day to 

 day. 



Examine first a dry seed, and notice the color and texture of its 

 covering (seed-coat, or testa). At the pointed end is the hilum and 

 inside this is a small hole, the micropyle this is best seen in a 

 soaked seed. 



Open a soaked squash seed (this can easily be done by first cutting 

 around the edge of the flattened seed, and then inserting the knife 

 and prying it open) . Remove the green covering from the "kernel," 

 and examine the embryo. At the small pointed end is the hypocotyl. 

 Separate the two cotyledons from each other and note that they are 

 fastened together only at the hypocotyl. Follow development of 

 squash seeds planted in soil, in tumbler as in 81, and laid on paper 



