1 76 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. f^entenatii, 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 oppor- 

 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 A. selaginoides is the first of the 

 succeeding third pair. 



As in many genera of Coniferce 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 antheree, although they usually present a foliaceous character, and 

 the thecse 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 Cupressinece and Taxinece, 

 where the thecae 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 thecse 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 

 1)0 suture or determinate line of dehiscence, although they are found to burst 



