NATTJRAI, ORDEE OF PLANTS. 185 



Sexual, or Flowering Plant*. 

 Fructification springing from a thallus .......*. Ml. RHIZCQ 



4< Foremost among the more perfect races comes a most anomalous collection of species called 

 Rhizogens. These plants, leafless and parasitical, have the loose cellular organization of 

 Fungi ; a spiral structure is usually to be found among their tissues only in traces. Some 

 of them spring visibly from a shapeless cellular mass, which stands in place of stem ana 

 root, and seems to be altogether analogous to the Thallus of the Fungi ; and it is probable 

 that they all partake in this singular mode of growth. Their flowers are like those of 

 more perfect plants ; their sexual apparatus is complete, but their embryo, which is not 

 furnished with any visible radicle or cotyledons, appears to be a spherical or oblong homo* 

 geneous mass." 



Fructification springing from a stem. 



Wood of stem youngest in the centre ; cotyledon single. 



Leaves parallel- veined, permanent ; wood of the stem always 

 confused iv. ENDOGENS. 



** Endogens consist of species whose germination is endorhizal, whose embryo has but one 

 cotyledon, whose leaves have parallel veins, and whose trunk is formed of bundles of spiral 

 and dotted vessels, guarded by woody tubes, which bundles are arranged in a confused 

 manner, and are reproduced in the centre of the trunk." 



Leaves net-veined, deciduous ; wood of the stem, when peren- 

 nial, arranged in a circle with a central pith V. DICTYOGEKS. 



" Dictyogens are Endogens, but with the peculiarity that the root is exactly like Exogens 

 without concentric circles, and the leaves fall off the stem by a clean fracture, just as in 

 that class." 



"Wood of stem youngest at the circumference, always concentric ; 

 cotyledons 2 or more. 



Seeds quite naked vi. GYMNOGENS, 



* 4 Gymnogens are a division of Exogens which, in the sexual apparatus, have no style ana 

 stigma, but are so constructed that the pollen falls immediately upon the ovules, a pecu- 

 liarity analogous to wtiat occurs among reptiles in the animal kingdom." 



Seeds inclosed in seed-vessels vn. EXOGENS. 



" The class at Exogens is composed of innumerable races, having an exorhizal germination, 

 an embryo with two or more cotyledons, leaves having a net- work of veins, and a trunk 

 consisting of woody bundles, composed of dotted and woody tubes, or of woody tubes alone, 

 arranged around a central pith, and either in concentric rings or in a homogeneous mass, 

 but always having medullary plates forming rays from the centre to the circumference, 

 and reproduced on the circumference of the trunk, whence their name of Exogens." 



CLASS I. THAXLOGETCS. 939 Genera ; 8394 Species. 



ALLIANCES OF THALLOGENS. 



L AKUT,M. Cellular flowerless plants, nourished through their whole surface by the medium in 

 which they vegetate ; living in water or very damp places ; propagated by zoospores, 

 coloured spores, or tetraspores. 283 Gen. ; 1994 Sp. 



Natural Orders. 1. Diatomacese, or Brittleworts. 2. Confervacese, or Confervas. 3. Fuca- 

 cese, or Seaweeds. 4. Ceramiacese, or Rosetangles. 5. Characea, or Charads. 



