AMENTIFEROUS PLANTS. 333 
fibre, composed of dotted woody tubes alone; arranged round a 
central pith, forming either in eccentric rings, or in a homogeneous 
mass, but always having medullary plates radiating from the centre 
to the circumference, which are reproduced on the circumference 
of the trunk. Genera, 6,191; species, 66,225. 
All botanists are agreed that the organs of reproduction may be 
expected to furnish the best characters for classification after those 
necessary for nutrition. Linnzus was of this opinion, and he made 
them to a considerable extent the basis of his system, but he 
mainly relied upon their number. The importance of the stamens 
and pistil did not escape the observation of Jussieu, who separated 
from all other Exoczns those having the stamens in one flower 
and the pistil in another, and he called them Dicurnovs. By this 
means he brought together a collection of natural orders corre- 
sponding with the monecious and diccious plants of Linnaeus. 
But, in carrying out his system, he excluded a vast number of 
truly diclinous plants. Some of these anomalies have been cor- 
rected by recent observers, and Dr. Lindley has divided the whole 
of the vast class of Exogens into (1) Dicirnous, (2) Hyroernovs, 
(3) Pertexnous, and (4) Epieynous Exocens. 
* : 
Sup-Ciass I.—Diciinovus EXOGENS. : 
HAVING MALE anp FEMALE, WITHOUT ANY TENDENCY TO BISEXUAL FLOWERS. 
— . flowers mane =. without or with only one floral —— ' 
‘uperior, embryo small, little or no albumen; ovary one-celled, aarinacese 
oak of pies or two ascending, radicle ascendin on : 
Ovary one-celled, ovules ‘ eee Fs 
one, pendulous, radicle superior, including . 
the Maples, the Alder, Birch, plane trees, &c. } LXXVIIL. Betulncee. 
-yielain® (W0-celled, with numerous winged seeds, including the Balsam : 
Liaend tree €s with many-seeded capsules, and the several species of } LXXIX. Attingiacem. 
g. This includes the She- 
- tan. ry one-celled, with humerous cottony seeds growing at the base of a : 
“alved capsule, as in Willows and ow Hho — } LXXX. Salicacer. 
fragran| lled, with a single erect seed and superior radicle. The 
tuales of America, the Cape, and India are aromatic shrubs or | yxyxy, Myricacee. 
2 te for hops 
8nd flowers elled, with @ single ascending ovule, an inferior radicle, e 
BOWS extensine nes bisexual. The beautiful and fragrant Oleastro ¢ LXXXII. Oleagnaces. — 
ae ely over the Northern Hemisphere, down to the Equator. _ 
The AMENTALEs are declinous Exogens with unisexual flowers, 
__. Mmentaceous inflorescence, and incomplete calyx. These cha- 
: ee form an obvious bond of union in this important natural — 
og P; and a brief description of the Berutacz, or Birches, and 
'CACE®, or Willows, are the most familiar examples we can 
