49 2 CLASSIFICATION. 



dom. The Plant Kingdom is then divided into a number of 

 subkingdoms as follows: ist, Subkingdom Thallophyta, the 

 thallus plants, including the Alga? and Fungi; 2d, Subkingdom 

 Bryophyta, the moss-like plants, including the Liverworts and 

 Mosses; 3d, Subkingdom Pteridophyta, the fern-like plants, 

 including Ferns, Lycopods, Equisetum, Isoetes, etc.; 4th, Sub- 

 kingdom Spermatophyta, the seed-plants, including Gymno- 

 sperms and Angiosperms. Subkingdoms are divided into groups 

 of lower order down to the classes. So there are subclasses, 

 subfamilies or tribes, subgenera, and even subspecies. But 

 taking the principal taxonomic divisions from the greater to the 

 lesser rank, the order would be as follows: 



Plant Kingdom. 



Subkingdom, Spermatophyta. 



Group (not used in a definite sense). 

 Class, Gymnospermae. 

 Order, Finales. 

 Family, Pinaceae. 

 Genus, Pinus. 



Species, strobus, or, in full, 

 Pinus strobus, the white pine. 



Group Angiospermae. 

 I. CLASS MONOCOTYLEDONES. 



941. Order Pandanales. Aquatic or marsh plants. The 

 cattail flags (Typha) and the bur- reeds (Sparganium), each rep- 

 resenting a family. The name of the order is taken from 

 the tropical genus Pandanus (the screw-pine often grown in 

 green-houses). 



942. Order Naiadales. Aquatic or marsh herbs. Three 

 families are mentioned here. 



The pondweed family (Naiadaceae) , named after one genus, 

 Naias. The largest genus is Potamogeton, the species of which 

 are known as pondweeds. Ruppia occidentalis occurs in 



