1C4 



THE CLASSES DIDYNAMIA AND TETKADYNAMIA. 



Fig. 342. 



Fier. 342. Didynamia Angiospermia. 

 Fig. 343. Didynamia Gymnospermia. 



a manifest capsule. It is requisite to remark, that when Linnaeus founded his classi- 

 fication, the seeds in the order Gymnospermia were believed to be naked ; but more 



recent investigation has shown that they were 

 inclosed in a flattened two or four-celled 

 ovarium. This, therefore, is an incorrect 

 division of the class ; but it has its value, 

 since the seeds, as they lie at the bottom of 

 the ovarium, seem to be naked. 



$'JTVJ _Jlf1ll!IIIM^F There is a further general characteristic 



$ \ '^^^Jlllk*'^^' ^ *kis C ^ ass v * z "> *^ e l^iate or bilabiate 



corolla (page 115), which is found in the 

 major part of its members. 



There are thirty -four genera, and eighty- 

 five species, in the class Didynamia, and 

 of these twenty genera are arranged in the order Gymnospermia. The calyx is two- 

 lipped in six genera viz., the Origanum or Marjoram, Thymus or Thyme, Prunella, 

 Scutellaria, Melittis, and Clinopodium ; but it is nearly regular, and divided into five 

 segments in the major part of the order, as the Mentha (Peppermint, Spearmint, 

 Bergamot-mint, Pennyroyal, &c.), Nepeta or Catmint, Marrubrium or Horehound, 

 Betonica or Wood Betany, Leonurus, Glecoma or Ground Ivy, Lamium or Dead 

 Nettle, Galeopsis, Teucrium or Wood Sage, and others. Nearly the whole of the 

 members of this order are common way-side and water-side plants ; but they possess 

 valuable medicinal properties, as in the essential oils found in little reservoirs of the 

 leaves of the Mentha, Origanum, and Thymus ; and a bitter principle, which is well 

 known to herbalist housewives, residing in the Marrubium, Betonica, and others. It is 

 probable that no member is decidedly poisonous. 



The order Angiospermia differs not only in having an evident capsule, but in the 

 possession of poisonous qualities, at least in several of its members, and is an instance 

 in which plants of diverse affinities have been improperly arranged together under the 

 same head, simply because one point in their organization seemed to indicate a resem- 

 blance. 



The number of sepals is again a mark of distinction. Thus the genus Orobanche 

 has but two sepals, whilst the Euphrasia or Eye-bright, Rhinanthus or Fellow Eattle, 

 Lathraea, Bartsia, and Melampyrum, have four segments of the Calyx, and eight have 

 the Calyx five-cleft. The last division contains the most important members of the 

 order, and of these the Digitalis, or Foxglove, takes precedence. That plant yields a 

 product from its leaves which is of great value in medicine, and which on many occa- 

 sions has inadvertently produced death. There are also the Scrophularia or Figwort, 

 common in ditches and on banks, Antirrhinum or Snapdragon, Linaria or Toad Flax, 

 Pedicularis or Lousewort, and the modest Linnsea Borealis, named after the great 

 founder of this system. 



None of the members of this order possess the aromatic properties mentioned in the 

 preceding order ; but there are several which add much to the gaiety of our fields and 

 shady lanes. In neither order are there any plants which afford nutriment to man. 



CLASS XV. TETRADTNAMIA. 



This class resembles the last, inasmuch as it has stamens of different lengths ; but it 

 differs in having four of them long and two short (Fig. 344). The two short ones are 



