PRACTICAL APPLICATION OF THE LINN^AN SYSTEM. 179 



determine the order of a plant without having first discovered the class in which it 

 ought to be placed ; for such was not the intention of Linnaeus when he founded his 

 arrangement. He will, therefore, first find the class and then the order ; but, in the 

 great majority of instances, both will be perceived by the same glance. 



But both the class and the order are alike dependent upon the presence of a flower ; 

 and therefore it will be in vain for the inexperienced student to attempt to discover 

 them, except at the proper season of the year, when the plant is in flower, and whilst 

 the flower remains perfect. 



These two preliminary circumstances are usually got over without any difficulty ; 

 but the next stages in the investigation require a far wider range of observation. It 

 is n ow necessary to examine, more or less minutely, every part of the plant. Thus 

 its height, and the size and form of its stem and root, must be noticed, distinguishing 

 between herbaceous or annual plants and woody, or those which are more or less perennial. 

 If the plant be herbaceous, it is necessary to ascertain if the stem be hollow, and if it 

 have any flutings or other markings upon its external surface ; and in all cases it is 

 requisite to glance hastily at the general arrangement of the leaves upon the stem or 

 plant. In reference to the root of herbaceous plants, it may further be observed that 

 its form must be noticed that is, as to whether it is tuberous or fibrous, or prcemorse, 

 or any other of the forms previously indicated. 



The leaves and the parts constituting the flower are, however, those parts from 

 which the distinguishing features of plants are usually drawn. 



The form of the leaf is a prime consideration ; and the student must notice if it is 

 round, oval, pointed, or otheiwise, and if equally so on each side of the midrib, and 

 also whether its edge is entire or divided in various ways. The size, thickness, and 

 colour should be regarded, and also the character of its surface, as to whether it is 

 smooth or rough, and if the hairs are distributed evenly over the two surfaces, or only 

 over one or over a part of one ; and also the precise characters of the hairs, as to whether 

 they are like bristles or down, or otherwise. Lastly, its venation demands attention 

 in order to show if the plant be an exogen, as indicated by the reticulated venation, or 

 an endogen, as shown by its parallel veins. The petiole, in like manner, must be ex- 

 amined, and afterwards the inquiry made if the leaf is caducous or permanent, and 

 if it altogether falls oft the stem or withers upon it, as is the case in the induviate con- 

 dition referred to in its proper place. The points in which leaves differ from from each 

 other are wonderfully numerous, probably extending to some hundreds ; and all of these 

 are made use of in describing the characters of plants. Most of them are happily 

 recognisable by the very apt terms with which this science, above all others, has been 

 supplied ; so that any inexperienced student, with a descriptive manual in his hand) 

 would scarcely fail to understand the terms which are employed to enable him to refer 

 any plant to its proper place. 



The flower is, as we have already shown, a compound organ, and offers a great many 

 objects to the student's attention. First, regard the general arrangement of the flowers 

 upon the plant, and inquire if they are placed in the axils of leaves (axillary) or other- 

 wise, and if they terminate a branch rendering it determinate. Then somewhat restrict 

 the range of observation, and notice that arrangement of the flowers upon the stem 

 which constitutes the inflorescence, and afterwards proceed to consider an individual 

 flower, regarding the envelopes from without inwards. The calyx and corolla may both 

 be monosepalous or polysepa 1 ous. If they are monosepalous, the form must be noticed as 

 to whether it is rotate or bell-shaped, or otherwise, and its free border inspected, to ascer- 



