GY US PLANTS. | 325 
from the ovules being uncovered, and the pollen communicated 
directly to the ovules without the intervention of stigma, style, or 
ovary. The plants comprehended in this great class agree with 
the flowering plants in having their vascular tissues complete, 
approaching the higher forms of vegetation in ‘the Joint-Firs, 
The Gnetacee combine the habit of growth of Chloranthus with 
the structure of their own class. With the Ferns and Club- 
mosses, some of the Cycadeacee agree in habit in the peculiar 
gyrate vernation of the leaves, and in the less perfect structure. 
. Of the spiral vessels and reproductive organs, some of them having - 
the gyrate vernation of the leaves of Ferns, along with the 
inflorescence peculiar to Conifers, and their habit of growth, 
although essentially the same as Exogens, yet resembling the 
growth of Acrogens in the lengthening of the terminal bud. In 
their mode of increase Gymnogens differ from other Exogens only 
by having a kind of tissue peculiar to themselves, in consequence 
of Which their wood presents large apparent perforations or disks, 
as in the Conifera. 
The Cycapgacr# are characterised by the cylindrical and un- 
hed growth of the trunk, and the development of one 
terminal bud, and by its dicecious flowers, the male flower generally 
gtowing in cones composed of peltate scales. In the Zamias, the 
female flowers are disposed in the same manner ; in the Cycasthey —— 
ate placed on the toothings of abortive leaves occupying the 
centre of the terminal bud. _ The leaves are pinnate, having some 
resemblance to those of Ferns and Palms; their wood is arranged 
™ numerous consecutive circles in Cycas, and also in a confused 
manner round the central pith, thus partaking of the peculiarities : 
both of the Exogens and Endogens. Mr. Robert Brown demonstrated 
the Similarity of conformation between the flowers of Cycas and 2 
iferee, and Adolphe Brongniart determined the resemblance 
between them in the structure of the vessels of their wood, thus 
Confirming the proximity of the former to Ferns; their relation 
the Conifer is established by both being cotyledonous, and 
: h their seeds having naked ovules, “constructed,” says Dr. 
“indley, “in a similar remarkable manner, and borne in both 
& “ses not upon an ordinary axis of growth, but upon the mo 
- face of metamorphosed leaves; the same peculiar form of a 
