CONIFERALES 



'345 



The reproductive structures in this group are extremely simple, 

 and the ovuliferous apparatus produces in maturity a single ovule. 

 In the genus Cephalotaxus of the Eastern Hemisphere an ovuliferous 

 strobilus is present in the early stage of development; this is 

 composed of scales each producing a pair of ovules a condition 

 comparable with that found in the Abietineae. As the develop- 

 ment of the seed progresses all but a single seminal structure 

 abort, so that in the 

 end no vestige of the 

 presence of a true fe- 

 male cone can ordi- 

 narily be observed. 

 In accordance with 

 the principle of re- 

 capitulation, we must 

 regard the young cone 

 of Cephalotaxus as in- 

 dicating the more 

 primitive condition 

 for the ovuliferous 

 apparatus in the 

 genus. Taxtis pre- 

 sents a marked con- 

 trast to that genus by 

 the fact that at no 

 time is the presence of a female or ovuliferous cone indicated. From 

 the first there is but a single ovule, and this is not related at any time 

 to a visible ovuliferous scale. The organization of the male cones in 

 the Taxineae is naturally less reduced than that of the female, in 

 accordance with the general principle of the conservatism of the 

 microsporangial apparatus in heterosporous groups. In the case of 

 the Taxineae the reproductive structures furnish convincing evidence 

 for the origin of the subtribe as the result of a process of reduction. 

 The structure of the wood in the Taxineae is quite characteristic. 

 The tracheids are marked by internal spiral bands which are of 

 late origin and are frequently for that reason designated as tertiary 

 thickenings (Fig. 251). Opposite pitting is present when the pores are 



FIG. 251. Semidiagrammatic view of the longitudi- 

 nal organization of the wood in the Taxineae. 



