176 Prof. Don’s Descriptions of two new Genera of the 
consist of a single verticil in the former, and two verticils in the latter, species ; 
or they are disposed in threes, as in C. Ventenatii, and the pericarpia then 
consist of two verticils or six pieces. In Pinus and other genera, the verti- 
cillate arrangement is completely re-established at the nodi, or points where 
the elongation of the internodes ceases, as is seen by the buds or branches, 
although the leaves themselves, from whose axils they proceed, are often 
. reduced to the condition of mere scales; and we may also remark, that the 
abortive branches of the Strobus tribe present a series of verticils of leaves, 
like the young seedling with its cotyledons. These facts, in my opinion, tend 
to overthrow the beautiful theory of the spiral development of the foliaceous 
organs, which has amused and puzzled the botanical world for some years past. 
I regret that in the only mature seed of Athrotaxis, which I had an opper- 
tunity of examining, the embryo had been destroyed by some insect ; but, from 
the leaves in A. cupressoides being in pairs, I conclude that the cotyledons are 
two, and that the fifth leaf of the spire in 4. selaginoides is the first of the 
succeeding third pair. Ü 
As in many genera of Coniferæ the pericarpia are seen to differ but little, 
either in form or arrangement, from the ordinary leaves of the plant, we 
should expect to find a corresponding simplicity in the structure of the male 
organs. The scales, as they are usually termed, of the male spike I consider 
to be the antheræ, although they usually present a foliaceous character, and 
the thecæ as parts of a simple anther, a portion only of the subcutaneous cel- 
lular tissue being apparently converted into pollen. In the greater part of 
the genera of this family, such, for example, as Cupressineæ and Tavinec, 
where the thecæ are arranged in a single series and situated at the external 
base of the scale, it would seem to be a portion of the under surface of 
the modified leaf that becomes transformed into pollen ; and this is also the 
case in Cunninghamia. On the other hand, in Dammara and Araucaria, 
where the thecz are numerous and disposed in a double series, a portion of 
both surfaces of the leaf may be supposed to be converted into pollen. On 
examining the scales or anthers at an early period, the masses of pollen will 
be found to present the appearance of small elevations occupying the lower 
base of the scale. At this period the raised portions of the cuticle present 
n? suture or determinate line of dehiscence, although they are found to burst 
