XLm] MORPHOLOGY OF CONES 115 



represents the lowest term of a series, the upper end of which is 

 represented by the scales of Agathis which have lost all external 

 signs of their supposed dual nature and retain only the inversely 

 orientated bundles as evidence of their descent from an ancestral 

 type in which the ovuliferous and bract-scales were separate 

 organs^. The scales of such genera as Sciadopitys, Aihrotaxis, 

 Cryptomeria (fig. 684, S, N, M), on this hypothesis, occupy an 

 intermediate position. The seminiferous scale of the Abietineae 

 is considered by many botanists to be a leaf or leaf-like organ 

 borne on an axillary shoot subtended by a bract, and it is believed 

 that the simple scale of Agathis has been produced by the 

 gradual fusion of two originally distinct organs. The Hgule of 

 Araucaria is held to be the outward and visible sign of the semi- 

 niferous scale that has almost lost its individuality, and with this 

 ligular reUc are homologised the upper half of the scale of Sequoia, 

 the deeply toothed upper part of the scale of Cryptomeria (fig. 

 684, M), the rounded ridge on the abaxial side of the seeds in 

 Athrotaxis (fig. 684, N), the membranous outgrowth on the scales 

 of Cunningkamia (fig. 684, K, m), and the seminiferous scale of the 

 Abietineae. It has been pointed out in support of this hypothesis 

 that two vascular bundles are given off from the axis of a Pine cone, 

 one of which forms the bract-scale bundles and the other the 

 vascular supply of the seminiferous scale^. 



In a recently published paper on the vascular anatomy of the 

 megasporophylls of Conifers by Miss Aase* additional facts are 

 given with regard to the origin and behaviour of the vascular 

 bundles of the cone-scales. In the upper part of a cone of Pinus 

 maritima the bract-supply arises as a single bundle at the base of 

 a gap in the stele, and the bundles of the seminiferous scale are 

 given off from the sides of the gap above the point of origin of the 

 bract-bundle : in the lowest sporophylls, on the other hand, the 

 bract and scale-bundles have a common origin. A separate origin 

 for bract and seminiferous scale-bundles is recorded in several 

 Abietineae and in some other Conifers. The origin of the vascular 



1 For references to literature on the morphology of cones, see Coulter and 

 Chamberlain (10); Worsdell (04) ; Rendle(04); Lotsy(ll); also CelakovskJ (82); 

 Kramer (85); Bayer (08); Aase (15). 



2 WorsdeU (99). ' Aase (15). 



8—2 



