xxxiv OUTLINES OF 



which may have taken a wrong fold or a bad direction. After this the pressure may 

 be gradually increased, and the plants left from one to several days without shifting. 

 The exact amount of pressure to be given will depend on the consistence of the speci- 

 mens, and the amount of paper. It must only be borne in mind that too much pres- 

 sure crushes the delicate parts, too little allows them to shrivel, in both cases inter- 

 fering with their future examination. 



240. The most convenient specimens will be made, if the drying-paper is the same 

 size as that of the herbarium in which they are to be kept. That of writing demy, 

 rather more than 16 inches by 10£ inches, is a common and very convenient size. A 

 small size reduces the specimens too much, a large size is both costly and inconvenient 

 for use. 



241. When the specimens are quite dry and stiff, they may be packed up in bundles 

 with a single sheet of paper between each layer, and this paper need not be bibulous. 

 The specimens may be placed very closely on the sheets, but not in more than one 

 layer on each sheet, and care must be taken to protect the bundles by sufficient cover- 

 ing from the effects of external moisture or the attacks of insects. 



242. In laying the specimens into the herbarium, no more than one species should 

 ever be fastened on one sheet of paper, although several specimens of the same species 

 may be laid side by side. And throughout the process of drying, packing, and laying 

 in, great care mast be taken that the labels be not separated from the specimens they 

 belong to. 



243. To examine or dissect flowers or fruits in dried specimens it is necessary to 

 soften them. If the parts are very delicate, this is best done by gradually moistening 

 them in cold water ; in most cases, steeping them in boiling water or in steam is much 

 quicker. Very hard fruits and seeds will require boiling to be able to dissect them 

 easily. 



244. For dissecting and examining flowers in the field, all that is necessary is a pen- 

 knife and a pocket-lens of two or three glasses from 1 to 2 inches focus. At home it 

 is more convenient to have a mounted lens or simple microscope, with a stage holding 

 a glass plate, upon which the flowers may be laid ; and a pair of dissectors, one of 

 which should be narrow and pointed, or a mere point, like a thick needle, in a handle; 

 the other should have a pointed blade, with a sharp edge, to make clean sections across 

 the ovary. A. compound microscope is rarely necessary, except in cryptoganiic botany 

 and vegetable anatomy. For the simple microscope, lenses of J, ?, 1, and 14 inches 

 focus are sufficient. 



245. To assist the student in determining or ascertaining the name of a plant be- 

 longing to a Flora, analytical tables should be prefixed to the Orders, Genera, and 

 Species. These tables should be so constructed as to contain, under each bracket, or 

 equally indented, two (rarely three or more) alternatives as nearly as possible contradic- 

 tory or incompatible with each other, each alternative referring to another bracket, or 

 having under it another pair of alternatives further indented. The student having a 

 plant to determine, will first take the general table of Natural Orders, and examining 

 his plant at each step to see which alternative agrees with it, will be led on to the 

 Order to which it belongs, he will then compare it with the detailed character of the 

 Order given in the text. If it agrees, he will follow the same course with the table of 

 the genera of that Order, and again with the table of species of the genus. But in 

 each case, if he finds that his plant does not agree with the detailed description of the 

 genus or species to which he has thus been referred, he must revert to the beginning 

 and carefully go through every step of the investigation before he can be satisfied. A 

 fresh examination of his specimen, or of others of the same plant, a critical considera- 

 tion of the meaning of every expression in the characters given, may lead him to detect 

 some minute point overlooked or mistaken, and put him into the right way. Species 

 vary within limits which it is often very difficult to express in words, and it proves 

 often impossible, in framing these analytical tables, so to divide the genera and species, 

 that those which come under one alternative should absolutely exclude the others. 

 In such doubtful cases both alternatives must be tried before the student can come to 

 the conclusion that his plant is not contained in the Flora, or that it is erroneously 

 described. 



