38o 



MORPHOLOGY OF GYMNOSPERMS 



far enough to contain embryo sacs (fig. 427). In the rare cases 

 when they function, the three envelopes are said to develop (15), 

 but, as shown in the preceding figure, only two envelopes may 

 appear in ovules which have enlarged considerably. Karsten (9, 



Figs. 425-427. — Gnetum Gnemon: longitudinal sections, showing bract with cluster 

 of flowers in the axil; fig. 425, ovule in ovulate strobilus with two integuments and 

 perianth; beneath the ovule is a dense tuft of hairs, so compact that they sometimes 

 appear like a tissue; fig. 426, sterile ovule in staminate strobilus, showing only two 

 envelops (inner integument and perianth); the oldest stamens are at the top, and in 

 longitudinal radial section usually show only one sporangium (as in the third stamen 

 from the top); fig. 427, section from staminate strobilus, in which the ovule has 

 developed to the free nuclear stage of the endosperm; all X23. 



II, 12) has found that the middle envelope always appears in a 

 rudimentary condition during the development of the incomplete 

 ovulate flowers, but gradually disappears. 



This confusion of interpretation has been cleared up (25) by a 



