CHARACTERISTICS OF PLANTS. 181 



been referred to when considering that organ, as well as those of more popular employ- 

 ment, committed to memory. 



All the foregoing particulars are not necessary to enable the student to determina 

 the genus of any plant, since the characteristic of a genus is, that it possesses only 

 certain (perhaps but few) features which are common to a number of other most 

 closely allied plants, which are thence termed species. But if any number of plants, 

 say ten, agree in certain features, so that they may be associat. d under one head, each 

 of these will differ from the others in features of greater minuteness ; and, consequently. 

 a more minute acquaintance with all the parts of a plant is more necessary to determine 

 the species than the genus. 



In order practically to apply these directions, we will give one or two familiar 

 examples, by way of illustration. Let us first examine the Myosotis, or Forget-me-not. 

 This plant will be found to have five stamens and one pistil, and consequently is at 

 once referable to the class Pentandria, and order Monogynia. Having referred to any 

 synopsis of the Linnaean arrangement, the student will find no fewer than forty genera 

 described under Pentandria Monogynia, and therefore will need further character- 

 istics, in order to prevent the necessity of comparing this plant with the descriptions of 

 all these genera. This is effected by noticing that a certain number of these genera 

 have an inferior monopetalous corolla, and two or four naked seeds ; and on referring 

 to the Myosotis he will find that such is the case with that plant also. This, then, 

 limits his investigation to ten genera, and it will be his duty to read the description of 

 each, beginning with the first, until he finus that one with which the plant in question 

 corresponds. The following are the characters of the genus Myosotis : 



" Calyx inferior, of one leaf, deeply five cleft ; segments acute, equal. Corolla of 

 one petal, salver-shaped ; mouth half closed, with five small valves. Filaments very 

 short ; anthers small, oblong. Ovary, four. Style, thread-shaped, central, as long aa 

 the tube ; stigma obtuse. Seeds egg-shaped, pointed, smooth." 



This description having been found to correspond with the plant under examination, 

 the next step will be to determine the precise species. The student will now find that 

 there are seven species described under that genus, and it will be his duty to compare his 

 plant with the first, and all others, until he finds the one with which it corresponds. 

 This will probably be far less tedious than it at first sight appears, since, immediately 

 he discovers in the description of any of the species any feature which differs clearly 

 from the specimen in his hand, he will not continue the comparison, but at once pro- 

 ceed to the description of the next species. In this way it is possible to examine a 

 dozen species in three or four minutes. Having, however, noticed that the description 

 of the genus and species Myosotis palustris corresponds with his plant, he has then 

 discovered that which he had been seeking for <m.,the class, order, genus, and species. 

 The characters of the species are thus described : 



" Calyx funnel-shaped, with short broad segments ; leaves oblong, roughish, with 

 close-pressed bristles, root creeping. Roots very long, creeping ; stem from six to 

 twelve inches high ; clusters many -flowered ; two or three together ; limb of the 

 corolla sky blue, the valves of the mouth yellow. Perennial ; flowers in June and 

 July; grows in marshy places and ditches : common." 



The student will thus be able readily to appreciate the different degrees of minuteness 

 needful to the determination of a genus and a species ; he will observe that the diffi- 

 culty of determining the genus and species is usually in proportion to the number of 

 genera found in the same class and order, and of species under the same genus. 



