Exercises XII and XIII 



THE ARRAY OF LIVING ORGANISMS 61 



THE PLANT KINGDOM 



Thallophytes _ 

 (nonvascular) 



Bryophyfes (mosses: 

 first lond forms; 

 thickened epidermis) 



Plant-like 

 protists 



Mostly extinct 



Sphenopsids 



(horsetails) 



Lycopsids 



(club mosses) 



Psilopsids 



_Tracheophytes_ 

 (vascular) 



Monocotyledons Dicotyledons 



(grasses) (others) 



L 



Angiosperms 

 (flowering plants: 

 enclosed seeds and fruits) 



Filicinae 

 (ferns: 



roots, stems, 

 leaves) 



Gymnosperms 



(conifers: dry 

 fertilization, seeds) 



Pteropsids 

 (leafy plants) 



extraordinary independence on occasion. A 

 sponge can be pressed through cheese cloth so 

 that all the cells are separated. Left to them- 

 selves, they reaggregate to form a new sponge. 



Stoneworts, though a small group, are the 

 most complex algae. You already know one of 

 them, Nitella. 



Lichens are composite associations of algae 

 with fungi, living together to their mutual benefit 

 (symbiosis), the alga photosynthesizing and the 

 fungus providing water and a source of nitrogen 

 for both partners. 



The slime molds display both plant-like and 

 animal-like characteristics, passing through 

 stages of free-living, unicellular flagellates and 

 amebae. Then the ameboid individuals mi- 

 grate together and form a great multinucleate 

 slug, bounded by a single membrane. This may 

 then differentiate into a beautiful fruiting body, 

 carrying a bulb containing spores at the end of a 

 long stalk, very plant-like in appearance. 



THE PLANT KINGDOM 



(Readings: S. P. T., Chapter 21. Weisz, Chapter 30. 

 Villee, Chapters 11 and 12. Optional readings are 

 C. P. Swanson, The Cell, Prentice-Hall, 1960, and 

 H. C. Bold, The Plant Kingdom, Prentice-Hall, 1960.) 



Principal groups and numbers of species 



Flowering plants (250,000) 



Conifers (600) 



Gingko (maidenhair tree) (1) 



Cycads (100) 



Ferns (9500) 



Horsetails (25) 



Club mosses (1000) 



Mosses (14,000) 



Liverworts (9000) 



Total : approximately 300,000 species 



