CHAPTER XVII 



ANGIOSPERMS 



DICOTYLEDONS 



SPOROPHYTES 



The sporophytes of the angiosperms include the common 

 herbaceous and woody-stemmed plants, such as the mandrake, 

 clovers, and elms, with which we became familiar in the first part 

 of the text. On account of the large amount of time already 

 devoted to the vegetative and reproductive structures of this 

 important group of plants it will only be necessary at this point 

 to review the knowledge already gained and to relate the life 

 history of angiosperms to the higher spore and seed plants which 

 we have recently considered. In this discussion the angiosperms 

 with two cotyledons in the embryo, namely, the dicotyledons, 

 have been chosen to represent the group, while the monocoty- 

 ledons will be reserved for a separate and special treatment. 



Structure. In connection with the following brief summary 

 of the important advances in anatomy made by the dicotyle- 

 dons the student should consult the figures and review the 

 text relating to the structure of woody and herbaceous stems 

 in Part I, and also the structure of Adiantum and the spruce 

 in Part II. 



The advances in structure relate mainly to the stem tissues, 

 since the leaves of dicotyledons are not much more highly 

 organized than those of ferns and cycads. 



The general arrangement of the stem tissues in the woody 

 types of dicotyledons is very similar to that of the spruce, and 

 the advances made by the spruce in this respect, as compared 

 with the pteridophytes, apply to the trees and shrubs among 

 dicotyledons. 



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