r 



176 PRACTICAL APPLICATION OF THE LINN^EAN SYSTEM. 



eartn, and in different localities bear very various relations to the total genera of plants ; 

 but it is certain that the most elegant, as well as the most lofty specimens, are not in- 

 digenous to our islands. Amongst the English genera we find the Polypodium, "Wood- 

 sia, Aspidium or Shield Fern, Cystea or Bladder Fern, Asplenium or Spleen Wort, 

 Scolopendrium or Hart's Tongue, Blechnum or Hard Fern, Pteris or Brake, Adiantum 

 or Maidenhead, Trichomanes, Hymenophyllum, and Osmunda or Flowering Fern. 



Before quitting the Linnsean arrangement, it may be advantageous to our readers if 

 we give a few simple directions as to the proper mode of examining a plant under this 

 system. 



The first aim of the botanist will be to determine the class and order in which 

 the plant under examination is arranged. He will, therefore, at once direct his atten- 

 tion to the flower (if the pknt do not belong to the last order, or that of Cryptogamia), 

 and see if both stamens and pistils are present together. If he find such to be the case, 

 the plant is bisexual ; but since, in the twenty-third class, or that of Polygamia, both 

 unisexual and bisexual flowers exist on the same plant, he will glance at other flowers 

 on the same stem, and ascertain if such be the case on the plant in question. If all the 

 flowers are bisexual, he will then attend to the number, length, and position of the 

 stamens, which, in a majority of instances, will at once direct him to the class sought 

 for. Thus, if there be two long and two short stamens in all the flowers, the plant is 

 Didynamous ; and if there be four long and two short stamens universally, he will 

 refer it to Tetradynamia. He must not, however, expect that in any plant all the stamens 

 shall be of precisely equal length ; but although such be the case, this will constitute 

 no important source of fallacy, since half-a-dozen examinations of the stamens of a 

 Didynamous and a Tetradynamous plant would enable him to perceive that the diversity 

 in length is not an accidental circumstance, but one which, from its constancy and 

 relative proportions, is very characteristic. Let him select the common Mint or Fox- 

 glove, as an example of Didynamia, and the Mustard or "Water-cress as an illustration 

 of Tetradynamia. 



This point having been passed, and having found that all the stamens are of nearly 

 equal length, he will next ascertain if they are separate from each other down to their 

 point of insertion. We will first suppose that their foot-stalks or filaments are connected 

 together through a distance more or less great, but yet so restricted that the anthers 

 are free ; the plant will belong to one of the three classes Monodelphia, Diadelphia, 

 or Polydelphia. He will next seek to determine if they form one set, or two or more 

 sets. To this end, he should take away the corolla, and any other parts which may 

 interfere with a due inspection of the base of the stamens ; and then with the fingers 

 try if any part of the mass of stamens will come away naturally, as it were, from other 

 parts. Thus the Hypericum, or St. John's-wort, possesses a large number of stamens, 

 which, on being gently pulled asunder at their bases, are readily detached in three or 

 four masses ; the stamens in each mass being still adherent, and each mass attached to 

 its neighbour simply by the cohesion of apposition. Such a plant, then, belongs to the 

 order Polydelphia. Again, the Pea, Bean, or Vetch presents the stamens arranged 

 precisely as exhibited in Figs. 221 and 351, except that the single stamen is not 

 so much detached from the mass as represented in these drawings ; and by examining 

 the concavity of the mass of stamens with the finger-nail, or any pointed instrument, 

 the odd stamen will be discovered lying close to the mass, but not connected with it. 

 This indicates the class Diadelphia. This class of plants has almost universally the 



