Assuming that the student has carefully read the Introductory part of this work, and is familar with the ordinary botanical terms, and the chief variations in plant structure as there set forth, it should, with the aid of the accompanying Key, he a very simple task to refer to its proper Family any Canadian wild plant of common occurrence. To illustrate the method of using this Key, let us suppose that specimens of the following plants have been gathered, and that it is desired to ascertain their botanical names, that is, the name of the Genus and the Species of each:- Red Clover, Strawberry, Blue Flag and Cat-tail Flag.
All of these produce flowers of some kind, and must therefore be looked for under the head of Flowering, or Phanerogamous, Plants.
With the specimen of Red Clover in hand, and the book open at page xii., we find that we have first to determine whether our plant is Dicotyledonous or not. The veining of the leaves suggests that it is so; and this impression is confirmed by the fact that the parts of the flower are in fives. Then, is the plant an Angiosperm? As the seed will be found enclosed in an ovary, we answer - Yes. Has the plant both calyx and corolla? Yes. Are the parts of the corolla separate? Here a little doubt may arise; but suppose we answer - Yes. Then our plant will be found somewhere in the Polypetalous Division. Proceeding with the enquiries suggested under this heading: - Are the stamens more than twice as many as the petals? We find that they are not.
Turn, then, to the heading marked B, page xv, "stamens not wore than twice as many as the petals." Under this we find two subordinate headings, designated by asterisks * and **. The first of these is not applicable to our plant. Under the second, marked thus **, we find two minor headings, designated by daggers,+and + +. The first of these, "Corolla irregular," is clearly the one we want. We have now, therefore, five families to select from. We cannot choose any one of the first four, because our plant has ten stamens, but the characters of the fifth are precisely the characters exhibited by Clover. Our Clover, therefore, belongs to the Order Leguminosae. Turning to page 50, and running through the "Synopsis of the Genera" as there given, we observe that No. 2, Trifolium, is the only Genus in which the flowers are in heads. Clover answers the description in the other respects also - viz.: "leaves of three leaflets,"and "stamens diadel-phous." Theonly question then remaining is, which Species of Trifolium have we in hand? Turning to page 52, we find we have eight Species to choose from. No. 2, Trifolium pratense, is the only one of them with purplish flowers. Trifolium pratense must, consequently, be the botanical name we are looking for.
Possibly the observer may decide that the parts of the corolla are not separate from each other, because in some instances it is really a doubtful question. He must then turn to page xvii, and under U. Gamopetalous Division, he must pursue his enquiries as before. Is the calyx superior? Plainly not. Proceed then to the heading B, "Calyx inferior." Are the stamens more than the lobes of the corolla? Yes. Then the choice of the six Orders in the section marked * is easily made as before, and the plant is referred to Legumlnosae.
Now let us take the Strawberry. As with Clover, we decide without difficulty that the plant is a Dicotyledon. The carpels are separate, and produce achenes in fruit; the plant must, therefore, be an Angiosperm. And there is no doubt that it is Polypetalous. As the stamens are very numerous it must come under the section marked A. Under this section we hare three subordinate headings, marked by one, two, and three asterisks, respectively. The stamensare clearly inserted on the calyx, and so our plant must be found under the heading marked **. "Without hesitation, we refer it to the Order Rosaceae. Turning to page 62, we find seventeen Genera to select from. A very little consideration will show us that No. 11, Fragaria, is the Genus we must fix upon. Referring to page 69, we have to choose between two species, Virginiana and vesca, and the choice is found to depend upon such obvious characters as to furnish no difficulty.
The leaves of Blue Flag are straight-veined; the parts of the flower, also, are in threes. We therefore decide that the plant is Monocotyledonous, and on turning to page xxii, we find three Divisions of Monocotyledons. The Flag clearly belongs to the Petaloideous Division. Then, is the perianth superior or inferior? Clearly the former. Next, are the flowers dioecious or perfect? Clearly perfect. And as the flower has three stamens, it must belong to the Order Iridaceae, described on page 235. The Genus is at once seen to be Iris, and the Species is determined without difficulty.
TheCat-tail Flagis also manifestly Monocotyledonous, from the veining of the leaves. But it is not Petaloideous. The flowers are collected on a more or less fleshy axis at the top of a scape. It therefore belongs to the Spadiceous Division, in which there are four Orders. The only practical question is, whether our plant belongs to Araceae: or Typhaceae. On the whole, we choose the latter, and find our decision confirmed on reading the fuller account of the two Orders on pages 217 and 219. The Genu3 is immediately seen to be Typha, and the Species latifolia.
These examples need not be extended here; but the beginner is recommended to run down, in the same manner, a few plants whose names he already knows. If successful in these attempts, he will naturally acquire confidence in his determinations of plants previously unknown to him.