THE SEED AND ITS GERMINATION 17 



of the pollen (a substance produced by the stamens) ^ on the 

 rudimentary seeds, known as ovules, borne within the divisions of 

 the three-lobed base of the pistil. 



3. Life history. The life history of every seed plant comprises 

 the series of changes which it undergoes in springing from a seed, 

 gro-wing to maturity, and producing flowers and seed of its own. 



THE SEED AND ITS GEEMINATION 



4. Germination of the squash seed.* * Soak some squash seeds in 

 tepid water for twelve hours or more. Plant these about an inch 

 deep in damp sand, pine sawdust, or peat moss, in a wooden box 

 which has had holes enough bored through the bottom to prevent 

 its holding water. Put the box in a warm place (not at any 

 time over 70°- 80° Fahrenheit, or 21°-27° Centigrade), and cover 

 it loosely with a board or a pane of glass. Keep the sand or 

 sawdust moist, but not wet, and the seeds will germinate. As 

 soon as any of the seeds, on being dug up, are found to have 

 burst open, sketch one in this condition, noting the manner in 

 which the outer seed coat .is split. Look for the peg, a kind of 

 knob, or hook, at the base of the hypocotyl, and see what it has 

 to do with the actions of the seedling. Continue to examine the 

 seedling at intervals of two days, until at least eight stages in 

 the growth of the plantlet have been noted. 



Observe particularly how the sand is pushed aside by the rise 

 of the young seedlings. Suggest some reason for the manner in 

 which the sand is penetrated by the rising stem. 



5. Examination of the squash seed.* * Make a sketch of the dry 

 seed, natural size. 



A. Note the scar at the pointed end of the seed where the 

 latter was attached to its place of growth in the squash. 

 Label this hilum. 



B. Note the little hole near the hilum; it is the micropyle, seen 

 most plainly in a soaked seed. 



1 In the nasturtium the pollen is a yellow, rather sticky powder. 



