GYMNOGENS. 221 



CLASS VL— GYMNOGENS. 



Synorhizse, Rick. Anal. duFr. Eng.ed. (1819).— Phanerogames Gymnospermes, Ad. Brongniart Veget. 

 Foss. 88. (1828).— Gjinnospermse, Nixiis Plantarum. 21. (1833) ; Ed. pr. p. 310. 



The plants comprehended in this class have nearly an equal relation to 

 flowering and flowerless plants. With the former they agree in habit, in 

 the presence of sexes, and in their vascular tissue being complete ; with 

 Ferns and Clubmosses, among the latter, some also accord in habit, in 

 the pecuHar gyrate vernation of the leaves of some Cycads, in then- sphal 

 vessels being imperfectly formed, and in the sexes being less complete 

 than in other flowering plants ; the females wanting a pericarpial covering, 

 and receiving fertihsation directly through the foramen of the ovule, without 

 the intervention of style or stigma, and the males sometimes consisting of 

 leaves imperfectly contracted into an anther bearing a number of poUen- 

 cases upon their surface. So great is the resemblance between Club- 

 mosses and certain Conifers, that I know of no obvious external character, 

 except size, by which they can be distinguished. Gymnogens are known 

 from most other Yasculares by the vessels of their wood having large appa- 

 rent perforations or disks. It is not, however, on this account to be under- 

 stood that they differ in growth from other Exogens ; on the contrary, they 

 are essentially the same, deviating in no respect from the plan upon which 

 Exogenous plants increase, but having a kind of tissue peculiar to themselves. 



At this point of the vegetable kingdom there is a plain transition from the 

 highest form of organization to the lowest. Gymnogens are essentially 

 Exogens in all that appertains to their organs of vegetation ; they have con- 

 centric zones in their wood, a vascular sj^stem in which spiral vessels are 

 found, and a central pith ; but they are analogous to reptiles in the animal 

 kingdom, inasmuch as their ova are fertilized by direct contact with the 

 male principle. The two most remarkable of the Orders are Conifers and 

 Cycads. Of these, the former is connected with Clubmosses among 

 Acrogens by means of the extinct genus Lepidodendron (see Fossil Flora, 

 vol. 2. t. 98), and their branches are sometimes so similar to those of certain 

 Lycopods themselves, as to leave no doubt of their relation. Compare, 

 for instance, Lycopodium Phlegmaria, and Cunninghamia sinensis. Some 

 Cycads have the gyrate vernation of the leaves of true Ferns, along 

 with the inflorescence of Conifers ; and their mode of forming their trunk, 

 although essentially the same as that of Exogens, yet resembles the growth 

 of Acrogens in lengthening by a terminal bud only. While, however, the 

 class of Gymnogens is thus distinctly marked by the most important physio- 

 logical peculiarities, it approaches the highest foims of vegetation by that 

 portion of it which bears the name of Joint-firs, plants, with all the structure 

 of their class, but with the manner of growth of Chloranths and Beefwoods, 

 which will be found in a future part of this classification. 



