142 MANUAlv OF NATURE STUDY. 



each grain of which is just as definite in form as a 

 grain of corn is definite, or a mustard seed is defin- 

 ite in form. As the form of seeds varies in differ- 

 ent plants, just so does the form of pollen vary in 

 different plants. So certainly is this true that 

 the plants may sometimes be determined by the 

 shape of the pollen alone. 



For examples of these different forms, see the 

 lily with its smooth, oval pollen grains ; the sun- 

 flower with its spherical pollen grains, beset with 

 prickly projections ; the musk plant pollen with its 

 spiral grooves, the evening primrose with its three 

 lobes as large as the central body, and so on, the 

 pollen grains of each kind of plant differing in 

 form from those of all others. But these forms 

 cannot be seen without the aid of a good micro- 

 scope. The other parts of the flower can be seen 

 very well with a good hand lens. Bvery pupil 

 ought to have such a lens in order to get best re- 

 sults from an examination of these delicate parts 

 of the plant. 



Note the opening of the anther. Does it open on 

 the inside next the pistil, or on the outside away I 

 from the pistil ? 



Now examine the pistil. Review the parts of 

 pistil as in third grade work and note the relation 

 of stigma and pollen to each other and to the 

 Qvules within the ovary. 



