PLANT CLASSIFICATION 159 



and differences in form, or size, or habit. True scientific 

 classification seeks to bring together into a given group all the 

 plants that are closely related to each other; that is, those 

 which are probably descended from common ancestors. In 

 the first place, all plants are divided into two great groups 

 known as seed-producing plants, and spore-producing plants. 

 The first is the group to which most of our attention has thus 

 far been given, and it embraces the herbs, shrubs, and trees 

 with which we are most familiar. We should bear in mind, 

 however, that many plants, like the palm and rubber plant, 

 which do not produce flowers in our climate, develop flowers, 

 fruits, and seeds when they are growing in their natural 

 home. Other plants with inconspicuous flowers for ex- 

 ample, grasses, elms, and pines also belong to this great 

 group of seed-producing plants. 



Sub-kingdom I, Seed-producing Plants (Optional) 



170. Gymnosperms and angiosperms. Seed-producing plants 

 are still further subdivided into two groups. The first group includes 

 all plants like the pines, hemlocks, and spruces, in which the seeds are 

 not produced in ovaries, but at the base of scale-like leaves which are 

 usually grouped together to form cones; hence the name cone-bear- 

 ing plants, which will apply to the common forms. The whole group 

 is known as gymnospenns (from Greek meaning naked seeds). 



Plants like beans, cucumbers, and pansies, on the other hand, 

 develop their seeds in ovaries, and these and all other plants of this 

 type constitute the second of the two sub-divisions, which is known 

 as the angiosperms (from Greek meaning having a vessel for seeds). 



171. Monocotyledons and dicotyledons. Again, the seed-pro- 

 ducing plants may be classified according to the number of coty- 

 ledons found in the seed. The corn, gladiolus, and lilies, for example, 

 have seeds with one cotyledon, and hence these are known as mono- 

 cotyledons (Greek, mono = one + cotyledon). Beans, peas, and 

 maples, on the other hand, have two cotyledons and are therefore 



