XVI DIBECTIONS TO TUE UNPRACTISED STUDENT. 



division is into three groups, marked A B. and C. Our plant, having dis- 

 tinct floral envelopes and neither spadix nor glumes, must belong to B., the 

 Petaloideous Division. This is subdivided into three sections, designated by 

 stars. The parts of the flower being all separate from each other, our plant 

 evidently falls under the third section, -with three stars, viz: "*** Perianth 

 wholly free from the ovary (inferior)." Next, as its perianth consists of three 

 green sepals and three colored petals, it belongs to the subdivision -t- -*-. 

 Under this there are four alternatives, 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, <fec., 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 Commelynacece. 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. Commdyna t 

 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. Tradescantla (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 proper 

 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, &e. 



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. Macrotys, and 2. Cimicifuga proper, 

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

 viz. 1. Sumac, 2. Toxicodejidron, 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. Cimicifuga racemosa, the Black Snake- 

 root ; Rhus qlabra, the Smooih Sumac, c. 



