XVI DIRECTIONS TO THE UNPRACTISED STUDENT. 



division is into three groups, marked A. B. and C. Of these B. alone has 

 "flowers with true floral envelopes," and therefore includes our plant. The 

 subdivision of B. is into "1. Flowers densely crowded on a spadix," and "2. 

 Flowers not on a spadix." Our plant falls under the latter. This is subdivided 

 into "* Perianth adherent to the ovary," and "* * Perianth free from the ovary." 

 Our plant accords with the latter. This is subdivided into four groups, with this 

 mark (-1- ), characterized by the nature of the perianth ; and it is evident that our 

 plant, having 3 green sepals, and 3 colored petals, and no glumaceous or husky 

 bracts, falls into the third group, *---. Under this there are four alterna- 

 tives, based on differences in the pistil. The numerous distinct pistils exclude 

 the first; the many or several seeds in each cell exclude the second; the one- 

 celled ovary, c. exclude the fourth ; while the third, having a single pistil with 

 a 2 - 3-celled ovary, and only one or two ovules or seeds in each cell, agrees with 

 our plant ; which we are thus brought to conclude must belong to the order 

 Comme/ynacece. The number, 485, affixed to this name, refers to the page in the 

 body of the work where this order is characterized. 



After comparing the plant with the ordinal character, especially with that por- 

 tion of it in italic type, and noting the agreement, let the student proceed to de- 

 termine the Genus. We have only two genera in this order, viz. : 1. Commelyna, 

 which has irregular flowers, petals unlike and on long claws, and the stamens 

 of two sorts, only three of them bearing perfect anthers, all of which is very 

 different from the plant we are studying; and 2. Tradescantia (p. 486), with the 

 characters of which our plant will be found perfectly to accord. 



Let the student then proceed to ascertain the Species, of which three are de- 

 scribed under this genus. Of the two sections, marked with stars ( * ), our 

 plant belongs to the first, having a sessile umbel. And of its two species, a 

 comparison with the characters of each fixes our plant as belonging to the first, 

 viz. T. Virginica. 



The abbreviated name or letter after the name of the genus and that of the 

 species, denotes the founder of the genus or the species ; in this instance Lin- 

 naeus, whose name is indicated by the abbreviation L. 



Whenever an order comprises several genera, a synopsis of them is given, like 

 that of Ranunculacece, p. 2, by the aid of which the student will readily deter- 

 mine the genus of the plant under examination. The number prefixed to the 

 name of the genus, in the synopsis, is that under which it stands, farther on, in 

 the full account. The genera in the synopsis are often ranked under their prope? 

 Tribes, or Suborders, &c. ; and the student will first determine the Tribe, or 

 other great group to which the plant he is examining belongs, and then the 

 Genus under that tribe, &c. 



Sometimes a genus embraces two or more strongly marked sections, or Sub- 

 genera, which are designated by the mark followed by a name. For example, 

 Cimicifuga, p. 14, has two subgenera, 1. Macrofys, and 2. Cimicifuga proper, 

 each with its own characters ; and the genus Rhus, p. 76, has three subgenera, 

 viz. 1. Sumac, 2. Toxicodendron, and 3. Lobadium. These names, how- 

 ever, do not make a part of the appellation of a plant, which is called by its 

 generic and its specific name only; as. Cinn'rifnga nicemosa, the Black Snake 

 root; Rhm glabra, the Smooth Sumac, &c. 



