LOCOMOTION OF SEEDS 175 



Books relating to it may be found cited in Chapter VII. 

 Other adaptations in seeds may also be taken up, such as their 

 protection against animals until ripe ; how they absorb water ; 

 how some seeds plant themselves, etc. 



For the essay on the seed, consult the advice in Chapter IV. 

 It is convenient to have a special book for the essays, uniform 

 with the laboratory book. After they have done their best on 

 this essay, it is well to read them one written by the teacher as 

 a model. Following is one I have read for this purpose to my 

 students : 



THE SEED 



General Function. 



Structure, Coats, Embryo, Endosperm. 



Locomotion. 



The seed is a portion of plant substance specialized for 

 reproduction and locomotion. Under a great variety of forms, 

 sizes, and colors, seeds have in common the coats, embryo, 

 and endosperm. The coats, one or two, are protective, and 

 the outer usually shows the scar of attachment to the pod 

 (hilum), a pit by which the fertilizing pollen tube entered 

 (micropyle), and a ridge through which the nourishment was 

 distributed (raphe and chalaza). The embryo is the young 

 plant, and consists of stem (hypocotyl), on which are placed 

 laterally one or two leaves (cotyledons), and which merges 

 upwards into the bud (plumule). The endosperm may be 

 stored in the cotyledons, making them thick, or around them, 

 or in both ways. 



Locomotion is as essential to plants as to animals, and since 

 the adults cannot move, the seed is generally used as the 

 locomotive stage, and to it appendages are added to cause it 

 to be carried by some of the natural moving agencies. These 



