178 PRACTICAL APPLICATION OP THE LINN^EAN SYSTEM. 



When there is a decrease in the number of stamens, it is usually accompanied by a 

 corresponding and equal increase in the number of the petals, and is for the most pan 

 restricted to the two classes Icosandria and Polyandria. If in either of these cases the 

 petals are more than five in number, it may be inferred that the innermost rows have 

 been produced at the expense of the outermost rows of stamens. This, however, 

 constitutes no sort of difficulty, since a sufficiently large number of stamens remain to 

 enable the student to determine the class, except in the case of cultivated plants, when 

 the whole of the stamens may have been converted into petals, as in the perfect Rose 

 (Fig. 207). We therefore advise the beginner to avoid all garden flowers, and examine 

 only those which are met with in their wild and uncultivated state. 



The classes Moncecia and Diceica are not so readily discovered by a reference to the 

 stamens of the flower, since for the most part the flowers are small, and without gay 

 colours, and the stamens are indistinct. He will first strive to ascertain if the flower 

 under examination has stamens or pistils (since it is unisexual), and will find that the 

 pistils occupy a central position, and have an expanded base or ovary, whilst the stamens 

 are usually arranged in a circle, leaving a central vacuity, and are surmounted by a 

 swollen part or anther. This is not at all times an easy diagnosis in practice ; but it 

 will aid the student to remember that, for the most part, the members of these classes 

 are large wooded trees. There are many exceptions to this rule, as in the cases of the 

 Stinging Nettle and the Sedges ; but the exceptions are perhaps less difficult of 

 diagnosis than the members which may constitute the rule. 



Having thus discovered the Class to which the plant belongs, he will next seek the 

 Order ; and to this end will chiefly regard the pistils. This will apply perfectly to all 

 plants having the stamens separate from each other, and of equal size ; and in euch 

 cases it suffices to count the number of pistils only. The orders of the first fourteen 

 classes are determinable in this way ; but beyond these, the pistil is not regarded in 

 determining the class. If, therefore, the plant belong to the class Polyandria, or any 

 other preceding class, simply count the number of pistils in order to find the order ; 

 but if it be Didynamous, or Tetradynamous, the student must notice the character of 

 the seed-vessel or pod. Thus, when a Didynamous plant has an evident more or less 

 conical ovarium, as in the Digitalis and Scrophularia, the order is Angiospermia ; bnt 

 if, after tearing away the corolla, he look deeply to the bottom of the calyx, and find a 

 flattened ovarium with one or two transverse lines on its surface, indicating a division 

 of the ovarium into two or four parts, as in the Mint, the plant belongs to the order 

 Gymnospermia. The diagnosis of the two orders in Tetradynamia is somewhat more 

 arbitrary ; for it depends simply upon the size of the pod. A long pod, as of the Pea, 

 indicates the order Siliquosa ; and a short, and for the most part a comparatively broad 

 one, marks the order Siliculosa . 



The orders found in the classes Monodelphia, Diadelphia, and Polydelphia, and also 

 Gynandria, Monoecia, and Dicecia, are determined by counting the number of the 

 etamens ; whilst those of Polygamia are simply Moncecia or Dicecia. The numerous 

 class Syngenesia is divided into orders without exclusive reference to its stamens 

 or pistils, but simply by the arrangement of the florets upon the capitulum. Thus, in 

 the order Polygamia JEqualis, all the florets are equal, and all possess both stamens and 

 pistils ; whilst the term Superflua indicates that the florets are divided into those of the 

 ray and of the disk, and that the former have pistils only. In the third order, or that 

 of Frustranea, the florets of the ray are destitute of both stamens and pistils. 



Thus we have not been able to give such directions as shall enable the student to 



