222 



MORPHOLOGY 



the stamen is peltate (as in taxads), and one-sided peltate (as in Tor- 

 reya). The sporangia are developed as usual, and in the Abietineae the 

 pollen grains (microspores) are winged (as in podocarps, fig. 489). 



Ovulate strobilus. — The ovulate strobilus of Pinaceae has been the 

 subject of much discussion. In the Abietineae the strobilus is made 

 up of a series of bracts, in the axil of each of which a so-called ovulif- 

 erous scale appears, which usually bears two ovules whose micropyles 

 are directed towards the base of the scale (fig. 490). In the other tribes 

 the bract and ovuliferous scale are more or less united. The discussion 



Figs. 491, 492. — Archegonium complex of Thuja: 491, group of archegonium 

 initials; 492, two mature archegonia (reached by a pollen tube, in which the body cell 

 has not yet divided) with a common archegonial chamber and a common archegonial 

 (nutritive) jacket. — After Land. 



referred to has to do with the nature of the ovuliferous scale, and many 

 facts indicate that it represents a fused pair of leaves of a dwarf axillary 

 branch. This means that the ovules are borne in the strobilus on axes 

 of the second order, as in Cordaitales, and that the ovulate strobilus of 

 Pinaceae is a compound strobilus. 



Ovule. — The structure of the ovule is as described for Taxaceae, 

 except that the outer fleshy layer does not develop, and the seed is dry ; 

 that both sets of vascular strands have been eliminated ; and also that 

 there is the same elaborate nutritive mechanism that was described 

 for Ginkgo. The development of the ovule and the seed is usually 



