Natural Family of Plants called Coniferse. 175 



concrete, and by a comparison with the proper leaves, I think there can remain 

 no doubt of their origin. The apex of the supposed concrete bracte is free, 

 and in the mature cone overlaps the summit of the placentary region, which 

 is situated on the inner surface of the scale, near its apex, and which at that 

 period is found greatly enlarged. The rapid enlargement of the placentary 

 region prevents the ovula, which are always situated on its under side, from 

 assuming an erect position, and they are consequently obliged to take a 

 downward direction ; but in no case do they form any lateral adhesion with 

 their axis, and there is consequently no raphe, and the foramen and point of 

 attachment retain their original position ; the ovula are, therefore, atropous ; 

 and the circumstance of the foramen occupying the lower extremity of the 

 seed, arises from the ovula being forced to take a downward direction by 

 the overhanging placenta. The hilum or point of attachment appears to be 

 placed a little obliquely on the inner base of the seed from the extension of 

 the winged border beyond it, which in this case consists of the cuticle merely 

 and not of the entire substance of the testa. The testa in Coniferce consists 

 of a single integument only, the secondine of Mirbel, as Mr. Brown pointed 

 out many years ago ; and what I described as a second integument in Pinus 

 bracteata and other species of the group of Silver Firs, is merely the cuticle of 

 the nucleus, which in all these species is very conspicuous, and similarly 

 winged like the proper testa, which by its open apex exhibits an analogy to 

 the testa or cupula of Tawus. 



The cotyledons in most Ccmiferce are verticillate, and we thei'efore con- 

 stantly observe a tendency to assume the same arrangement in the after 

 leaves and other organs derived from them ; but from the elongation and 

 unequal development of the axis, the verticillate disposition is departed 

 from, and they most frequently exhibit a spiral arrangement. A multitude 

 of such spires in close contact, as happens in the branches of Araucaria and 

 in the cones of Pinus, would of course give an indefinite appearance to the 

 series ; but in no case does the number of leaves in such a verticil exceed ten. 

 In Cupressus the cotyledons are two and opposite, and we constantly find the 

 after leaves opposite, the pairs crossing each other give to the leaves the 

 appearance of being arranged in four rows. In Callitris the leaves are ar- 

 ranged in fours, as in C. quadrivalvis and octovalvis, and the pericarpial leaves 



2a2 



