OUTLINE OF CLASSIFICATION 225 



relationships, into larger or smaller groups according to the grade 

 of relationship and the number of plants of any one kind. For 

 example, all plants which develop seeds are classified together 

 as the seed plants (Spermatophyta}. In the seed plants there are 

 two divisions: first, those in which the seeds are enclosed in the 

 ovary, the Angiosperms, and second, those in which the seeds are 

 on the outer surface of the carpel, or exposed, the Gymnosperms. 

 The Angiosperms are further divided into two subdivisions ac- 

 cording to the number of cotyledons on the seedling, the venation 

 of the leaves and arrangement of the vascular bundles, etc. (see 

 Chapter VIII), into the Monocotyledons and Dicotyledons. Smal- 

 ler subdivisions are made into classes, these into orders, these 

 into families, these into genera, and these into species. The 

 genus and species names together make up the name of the plant. 

 But species are often divided into subspecies, varieties and 

 forms. 



357. The plant kingdom and its subdivisions or branches. 

 All plants taken together constitute the Plant Kingdom. There 

 are a number of subdivisions of the plant kingdom, called Sub- 

 kingdoms or Branches. Each subkingdom includes a great 

 variety of plants, all of which agree in one or several general 

 characters or relationships. For example, all the seed plants 

 form one subkingdom known as the Spermatophyta or Sper- 

 matophytes* The seed plants have attained a higher degree of 

 development than any other branch. Next to the seed plants are 

 the ferns and fern-like plants, which constitute another sub- 

 kingdom known as the Pteridophyta^ or Pteridophytes. Next 

 below the pteridophytes stands the subkingdom Bryophyta-\ 

 or Bryophytes, which includes the mosses and moss-like plants, 

 i.e., the true mosses and liverworts. Below these is the sub- 

 kingdom Thallophyta^ or Thallophytes, which includes the 

 algae and fungi. This is the lowest subkingdom of plants 



* (nrep/ML = seed, <f>vrov = plant, 

 j" TTTpts=wing or fern, <f>vrov = plant. 

 | /3pvov = moss, <J>VTOV = plant. 

 0aAAos = thallus or frond, <f>vr6v = plant. 



