CHAPTER XVIII 

 THE SEED PLANTS i 



266. Introductory. In the earlier chapters of this book we 

 dealt only with flowering or seed plants, which belong to the 

 fourth great division of the plant kingdom. This division is 

 known as the spermatophytes, which means " seed plants." 

 In fact, our earlier discussions considered practically no plants 

 except members of the second of the two groups of seed 

 plants the angiosperms, or plants with inclosed seeds. The 

 other group of seed plants is the gymnosperms, or plants with 

 exposed seeds. Seed plants are the most conspicuous plants 

 of the earth, and are the ones which people ordinarily regard 

 as composing the plant kingdom. They are most important 

 in agriculture, horticulture, landscape and vegetable garden- 

 ing, forestry, and the industries. We shall first consider the 

 gymnosperms, of which there are over four hundred species, 

 some widely distributed and some limited to small areas. 



267. Gymnosperms the pine as a type. The pine is the 

 best general illustration of the gymnosperms and is by far 

 the most widely distributed member of the group. Sometimes 

 pines form dense forests of .tall, straight trees standing close 

 together. It is only when thus crowded that they grow tall, 

 since, when growing alone in open territory, they secure ample 

 light without attaining such a height. 



With a deep-growing central taproot and extensively 

 branched lateral roots the pine plant holds its place in the 



1 This chapter summarizes some of the things said about seed plants in 

 the first chapters of this book, and adds discussions which will enable the 

 student to see in an elementary way the relation of the seed plants to the 

 groups of lower plants discussed in the immediately preceding chapters. 



