120 



MORPHOLOGY OF SPERMATOPHYTES 



Tumboa. While the flowers are functionally monosporan- 

 giate, there is evidence of their derivation from a bisporan- 



giate condition. They are borne 

 in the axils of prominent opposite 

 bracts which form conelike stro- 

 bili. These strobili are produced 

 upon branching axes, which arise 

 from the crown above the foliage 

 leaves, or rarely beneath them. 

 The staminate flower consists of 

 two decussate pairs of free bracts, 

 forming the so-called perianth, 

 within which there is a whorl of 

 six (rarely five or four) monadel- 

 phous stamens, each of which is 

 capped by a group of three spo- 

 rangia. In the center is a single 

 sterile ovule, whose projecting 

 micropyle is spirally coiled and 

 has a flaring expansion at the tip 

 (Figs. 86, 87).* The whole struc- 

 ture is puzzling and anomalous 

 among Gymnosperms, for it seems 

 to indicate derivation from a per- 

 fect flower. The microsporangia also seem to be distinctly 

 foliar in origin. 



Gnetum. The flowers are monosporangiate and mostly 

 dioecious, the inflorescence being in the form of spikes of con- 

 nate bracts with numerous flowers in their axils. The stami- 

 nate flowers resemble those of Ephedra, consisting of two coher- 

 ent bracts investing a short axis which bears two sporangia. 

 Such evidence as we have indicates that these sporangia are 

 cauline (Fig. 88). 



THE MEGASPORANGIUM 



Ephedra. In the spicate inflorescence one or more ovulate 

 flowers occur in the axil of each bract. Each flower consists of 

 two more or less connate scales which invest a solitary cauline 



FIG. 87. Tumboa : A, staminate stro- 

 bilus ; J3, ovulate strobilus ; both 

 two thirds natural size. A from 

 the Bot. Mag., B after LE MAOUT 

 and DECAISNE ; the whole figure 

 from ENGLER and PKANTL'S Nat. 

 Pflanzenfam. 



* Excellent illustrations of the staminate and ovulate strobili may be found 

 in Gardeners' Chronicle III. 24 : 63. 1898. 



