THE CLASSIFICATION OF PLANTS. 79 



plants, which were formerly but little observed, have in con- 

 sequence of the careful investigations of recent times been 

 pi'oved to present such a great variety of forms, and such a 

 marked difference in their coarser and finer structure, that 

 we must distinguish no less than fourteen different classes 

 of them ; whereas the number of classes of flowering plants, 

 or Phanerogamia, may be limited to four. However, these 

 eighteen classes of the vegetable kingdom can again be 

 naturally grouped in such a manner that we are able to dis- 

 tinguish in all six inain divisions or branches of the vege- 

 table kingdom. Two of these six branches belong to the 

 flowering, and four to the flowerless plants. The table on 

 page 82 shows how the eighteen classes are distributed 

 among the six branches, and how these again fall under the 

 sub-Jcingdoms of the vegetable kingdom. 



The one sub-kingdom of the Cryptoganiia may now be 

 naturally divided into tivo divisions, or sub-kingdoms, differ- 

 ing very essentially in their internal structure and in their 

 external form, namely, the Thallus plants and the Prothallus 

 plants. The group of Thallus plants comprises the two 

 large branches of Tangles, or Algfe, which live in water, and 

 the Thread-plants, or Inophytes (Lichens and Fungi), which 

 grow on land, upon stones, bark of trees, upon decaying 

 bodies, etc. The group of Prothallus plants, on the other 

 hand, comprises the two branches of Mosses and Ferns, 

 containing a great variety of forms. 



All Thallus plants, or Thallophytes, can be directly recog- 

 nized from the fact that the two morphological fundamental 

 organs of all other plants, stem and leaves, cannot be dis- 

 tinguished in their structure. The complete body of all 

 AlgtB and of all Thread-plants is a mass composed of simple 



