394 



GYMNOSPERMS 



continual in the four parts of the perianth of the flower. There are 

 six trilocular stamens, one opposite each of the smaller bracts of the 

 perianth, and two opposite each of the larger ones. The stamens are 



borne on a tube, and below each stamen 

 is a protuberance, which can be a nectary 

 when one wishes to emphasize the resem- 

 blance to an angiosperm flower. 



The most remarkable thing about this 

 flower is that it is bisporangiate. In the 

 center is an ovule, with a well-developed 

 nucellus, but never with any sporogenous 

 tissue. There is an inner integument, 

 which elongates considerably, although it 

 never reaches the extreme length of the 

 inner integument of the ovulate flower. 

 However, the integument of this sterile 

 ovule has an expanded funnel-shaped tip, 

 which has caused some to write about 

 stigmas. Outside the inner integument is 

 the perianth, consisting of four bracts: 

 two at the ends, small and sharply angled 

 at the midrib, and two at the sides, par- 

 allel with the large bract in the axil of 

 which the flower stands. Thus, each flow- 

 er is a strobilus in the axil of a bract, and 

 the whole cone is a compound strobilus. 

 The parts of the flower are in two's or 

 four's. In those Cruciferae which have 

 tetradynamous stamens, the positions of 

 the two missing stamens are clearly 

 marked by nectaries. In Welwitschia the 

 two stamens at the ends, in the floral dia- 

 gram, are generally larger than the other 

 four, so that, if two stamens are really 

 missing, they would have alternated with 

 the two stamens opposite each of the larg- 

 er bracts of the perianth. No traces of 



Fig. 371. — Welwitschia mi- 

 rabilis; staminate flower: A, 

 longitudinal section of flower 

 with nearly ripe pollen : p, bract 

 of perianth; s, trilocular an- 

 ther; /, protuberance on inner 

 face of stamen tube; /, inner in- 

 tegument; ?/, nucellus of sterile 

 ovule; h, bract. B, floral dia- 

 gram: lettering as in A; I, axis 

 of cone. — From Coulter and 

 Chamberlain, Morphology of 

 Gytnms perms'^ (University of 

 Chicago Press). 



