DIFFICULTIES IN ANALYSIS. 129 



275. But the minuteness of the organs or parts to be 

 studied is often discouraging even to the accurate student, 

 much more to the careless one. To overcome this, skill in 

 dissection and a dauntless courage in observation are indis- 

 pensable. Moreover, there is often much ambiguity in the 

 nature of the subject. For example, whether the Geraniums 

 are herbs or shrubs ; whether the flowers of Petunia are reg- 

 ular or irregular ; whether the Pear leaf is ovate or oval, 

 &c. Experience will at length diminish this difficulty. 



276. The exact limits between the classes, the cohorts, &c., 

 are not always easily defined. For example, is Trillium an 

 Exogen or an Endogen ? Its netted leaves indicate the for- 

 mer, but its flowers being three-parted throughout, and its 

 seeds with one cotyledon, prove it to be an Endogen. Again, 

 is Spring Beauty an Exogen or an Endogen? Its leaves 

 seem, at first, parallel-veined, but as its flowers are five-parted 

 it is an Exogen. 



277. Angiosperms will be readily distinguished from Gym- 

 nosperms, if we remember that almost all the latter are ever- 

 green trees, like the Pines, Cedars, Larches, &c. 



278. The industrious student will very soon find himself 

 so well acquainted with the difi'erent characters of the cohorts 

 that he will in analysis refer his plant at once to its right 

 cohort, without consulting the previous parts of the table. 

 This is desirable; and a thorough acquaintance with the 



275. What of the minuteness of the organs of some plants ? What of the 

 ambiguity of the plants themselves ? What will soon diminish this diffi- 

 culty ? Mention examples of tliis ambiguity. 



276. Are the limits of the classes, cohorts, genera, &c., always clear? 

 How do wc know that the Trillium is an Endogen ? that Spring Beauty is 

 an Exogen ? 



277. How may the Gymnospenns be quickly distinguished? 



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