322 



MORPHOLOGY OF GYMNOSPERMS 



(150) it is made up of spirally arranged and imbricated bracts that 

 form an ovoid cone, and in Microcachrys a definite strobilus is formed 

 by the sporophylls, which occur in decussating cycles of four and thus 

 give the appearance of a spiral arrangement. The case of Torreya 



taxijolia (loi) may illustrate 

 the general situation. In this 

 form the strobili are borne in 

 the axils of the lower leaves 

 of short young shoots, usually 

 a pair of them on a short axil- 

 lary branch. In most cases 

 there is only a single pair of 

 strobili on a strobiliferous 

 shoot, but frequently there are 

 two pairs, and rarely three on 

 the same shoot. Therefore, 

 near the base of these shoots 

 two to six strobili may occur, 

 the upper pairs never maturing 

 and usually only one of the 

 lowest pair producing the large 

 plumlike seed (fig. 376). A 

 strobilus consists of four en- 

 veloping bracts and a single, 

 terminal, erect ovule, resem- 

 bling a simple ovulate flower 

 with a perianth of four bracts; 

 but these are evidently the 

 sterile bracts of a much re- 

 duced strobilus. The relation 

 of the strobili to the young 

 shoot is exactly comparable 

 to the arrangement of the staminate strobili, the difference being that 

 more of the latter mature and the stamens are numerous. In this 

 sense, the whole ovuliferous shoot may be regarded as corresponding 

 to the compound ovulate strobilus of the Abietineae. 



A general feature of Taxaceae, illustrated bv Torreya, is the 



Fig. 376. — Torreya laxifolia: ovulate 

 branch, April 7, 1904; natural size. — After 

 Coulter and Land (ioi). 



