XIV. DIVISION OF LABOR. THE VARIOUS FORMS OF 

 PLANTS AND ANIMALS 



Problems. The development and forms of plants. 

 The development of a simple animal. 

 What is division of labor ? In what does it result ? 

 How to know the chief characters of some great animal 

 groups. 



LABORATORY SUGGESTIONS 



A visit to a botanical garden or laboratory demonstration, Some of the 

 forms of plant life. Review of essential facts in development of bean 

 or corn embryo. 



Demonstration. Charts or models showing the development of a many- 

 celled animal from egg through gastrula stage. 



Demonstration. Types which illustrate increasing complexity of body 

 form and division of labor. 



Museum trip. To afford pupil a means of identification of examples 

 of principal phyla. This should be preceded by objective demonstration 

 work in school laboratory. 



Reproduction in Plants, Although there are very many 

 plants and animals so small and so simple as to be composed of 

 but a single cell, by far the greater part of the animal and plant 

 world is made up of individuals which 

 are collections of cells living together. 



In a simple plant like the pond scum, 

 a string or filament of cells is formed 



by a single cell dividing crosswise, the thread made up of cells ? 

 two cells formed each dividing into two 



more. Eventually a long thread of cells is tnus formed. At times, 

 however, a cell is formed by the union of two cells, one from each 

 of two adjoining filaments of the plant. At length a hard coat 

 forms around this cell, which has now become a spore. The 

 tough covering protects it from unfavorable changes in the sur- 



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