30 INTBODXTCTIOK. 



That of writing demy, rather more than 16 inches by 10^ inches, is a com- 

 mon and very convenient size. A small size reduces the specimens too much, 

 a large size is both costly and inconvenient for use. 



To examine the interior of flowers or fruits in dried specimens, it is neces- 

 sary 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 hot 

 water or in steam is much quicker. Very hard fruits and seeds wiU require 

 boiling to be able to dissect them easily. 



For dissecting and examining flowers in the field, all that is necessary is 

 a penknife and a pocket-lens of two or three glasses, from one inch to two 

 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 

 to be dissected may be laid, and a pair of dissectors, one of which should be 

 narrow and pointed, or a mere point Uke 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 unnecessary for the characters 

 given in this work. 



rv. Determination of Plants. 



The Analytical Keys of this work, or tables for finding out the names 

 of plants, contain under each bracket two alternatives (rarely three or more), 

 as near as possible contradictory or incompatible with each other. The 

 plant to be determined must be examined to see which of the two alterna- 

 tives applies to it, commencing with the first bracket of the general table, 

 and following through the bracket to which that alternative refers, and so 

 on till the name of the Order is arrived at. The plant must then be care- 

 fully compared with the description of the Order given in the Flora. If it 

 agrees, the same process must be gone through with the Analytical Key of 

 the genera of that Order to find the genus, and again with the key of the 

 species of that genus to find the species.* 



Suppose the plant to be a Dandelion, a Daisy, or a Thistle. On opening 

 what appears to be the fiower, we see at once that each part, which we may 

 at first have taken for a petal, contains a separate style, and has a separate 

 ovai-y (appearing like a seed) under it, but no separate calyx, aU these flo- 

 rets being collected within a common involucre. The flower is therefore 

 compound. Our attention is also called to the anthers. They may at first 

 escape the beginner, but with a little care they will be discovered forming a 

 ring rovmd the style. We may then conclude that our plant agrees with 

 the first alternative which refers to the second bracket. We must now 

 look to the ovary imder any one of the fiorets, cut it open, and, finding but 

 a single ovuLe or seed, we are referred to the great Order of Composites. 

 This second bracket is only necessary to exclude two or tliree Campanula- 

 ceous plants {Phyteuma and Jasione), which have the united anthers and 

 heads of flowers of Composites, but are most readily kno^n by the nume- 

 rous small ovules or seeds in their ovary or fi-uit. On turning to the de- 

 acription of the Order Composites, we are cautioned against confounding 

 with them two or three other plants which have similar heads of flowers, 

 and being satisfied we are right, we proceed in the same manner to find out 

 the genus of our plant. 



• In the tables of genera and species in this work, the alternatives, instead of being 

 bracketed together, are usually equally indented within the margin, a form more conve- 

 nient for reference when the genera so classed are not numerous. 



