188 BOTANICAL WOBK. [SECTION 19. 



way. It is well to make drawings or outline sketches of the smaEer parts, 

 and especially diagrams of the plan of the flower, such as tiiose of Fig. 

 225, 227, 241, 244, 275-277. For these, cross sections of the flower-bud 

 or flower are to be made : and longitudinal sections, such as Fig. 270-274, 

 are equally important. The dissection even of small seeds is not difficult 

 after some practice. Commonly they need to be soaked or boiled. 



575. The right appreciation of characters and terms used in description 

 needs practice and calls for judgment. Plants do not grow exactly by 

 rule and plummet, and measurements must be taken loosely. Difference 

 of soil and situation are responded to by considerable variations, and other 

 divergences occur which cannot be accounted for by the surroundings, nor 

 be anticipated in general descriptions. Annuals may be very depauperate 

 in dry soils or seasons, or very large when particularly well nourished. 

 Warm and arid situations promote, and wet ones are apt to diminish pubes- 

 cence. Salt water causes increased succulence. The color of flowers is 

 apt to be lighter in shade, and brighter in open and elevated situations. 

 A color or hue not normal to the species now and then occurs, which 

 nothing in the conditions will account for. A white-fioioered variation of 

 any other colored blossom may always be expected ; this, though it may be 

 notable, no more indicates a distinct variety of the species than an albino 

 would a variety of the human species. The numerical plan is subject to 

 variation in some flowers ; those on the plan of five may now and then vary 

 to four or to six. Variations of the outline or lobing of leaves are so familiar 

 that they do not much mislead. Only wider and longer observation suf- 

 fices to prevent or correct mistakes in botanical study. But the weighing 

 of evidence and the balancing of probabilities, no less than the use of the 

 well-ordered and logical system of classification, give as excellent training 

 to the judgment as the search for the facts themselves does to the observing 

 powers. 



§4. SIGNS AND ABBREVIATIONS. 



576. For a full account of these, whether of former or actual use, see 

 "Structural Botany" of the "Botanical Text Book," pp. 367, 392, as also 

 for the principles which govern the accentuation of names. It is needful 

 here to explain only those used in the Manuals and Floras of this country, 

 for which the present volume is an introduction and companion. They 

 are not numerous. 



577. In arranging the species, at least those of a large genus, the divi- 

 sions are denoted and graduated as follows : The sign § is prefixed to sec- 

 tions of the highest rank : these sections when they have names affixed to 

 them (as Prunus § Cerasus) may be called subgenera. Wiien the divi- 

 sions of a genus are not of such importance, or when divisions are made 

 under the subgenus itself, the most comprehensive ones are marked by as- 

 terisks, * for the flrst, * * for the second, and so on. Subdivisions are 



