CONIFERJE. 257 



in the axil of a leaf), And in this case the external integument of the 

 ovules is expanded into leaf-like bodies, which have united to form 

 one " symphyllodium " (ovuliferous scale) which is inverted so that 

 its dorsal side is turned upwards and bears the nucellus and 

 the other integument (" hemichlamydeous " ovules). The carpel 

 itself is therefore in this instance extremely reduced. The keel, 

 or (in Pinus) " mucro" (Fig. 268 jB), which is found in several 

 genera, represents then a third carpel, which is sterile. In the 

 other orders of the PinoideaB the cover-scales and ovuliferous scales 

 grow more and more together and finally form one structure, which 

 also is termed a " cone-scale," although from its development it 

 cannot be homologous with the cone-scales of the Abietaceas. 

 This connation is least in the TAXODIACEJ and ARAUCARIACE.E and 

 may be traced on the upper surface of the " cone-scale " by the 

 presence of a stronger or slighter ridge or pad, the free portion 

 of the ovuliferous scale (Figs. 256, 266, 269). It is most strongly 

 pronounced in the CUPRESSACEJ;, in which the two scales form one 

 single structure, the cone-scale (Fig. 274). The vascular bundles 

 in the under portion corresponding to the cover-scale, have the 

 xylem towards the upper side as usual in leaves, whilst the bundles 

 present in the upper side of the cone-scale, which thus represents 

 the ovuliferons scale, turn their xylem downwards. The hemi- 

 chlamydeous ovules are then situated on the upper side of this 

 cone-scale. According to this theory the CUPRESSACEJ appear to be 

 the youngest type, a view which corresponds with their vegetative 

 structure. If there is only one ovule in these orders as in Agathis 

 (Fig. 265) and Araucaria, then the flower is reduced to a single 

 carpel and one ovule, as in the case of Dacrydium and Microcachrys. 

 If two or more ovules are present, then the same number of carpels 

 may be supposed to exist, the external integuments of their 

 ovules being developed into leaf-like structures which collaterally 

 coalesce to form a " symphyllodium," or are suppressed. 



According to this theory, which is based on the researches of 

 Celakovsky, the female flowers of the Coniferte may be classed 

 thus : 



1. In all cases situated in the axil of a bract and collected into 

 cones, with numerous flowers or with few or one flower. In Ginkgo 

 only, are they situated in the axil of foliage- or scale-leaves. 



2. It is only in Taxus that bracteoles are present. 



3. They are formed only from rudimentary carpels, in which the 

 stem takes no part. 





