MORPHOLOGY 
The three genera differ widely in this regard, and therefore must be 
considered separately. 
Ephedra. The female gametophyte is developed as in other gymno- 
sperms, with free nuclear division (up to 256 nuclei), parietal wall 
formation, centripetal growth, and differentiation of the endosperm into 
distinct micropylar and antipodal 
regions. In this case, however, the 
antipodal tissue (nutritive) is rela- 
tively small-celled and compact, and 
the micropylar tissue is more loosely 
organized and has thinner walls. In 
this loose micropylar tissue usually 
two archegonia are formed, their 
very long, many-tiered necks extend- 
ing to the pollen chamber described 
530, 531. Gnetum Gnemon: 530, diagrammatic section of ovule, showing the 
two integuments (inner one forming the micropylar tube), nucellus with disorganized tip, 
and deep-placed embryo sac, beneath which is a mass of feeding (glandular) tissue; 
531, enlarged view of same embryo sac (ready for fertilization), in which the female 
gametophyte consists of free nuclei (each a potential egg), and below which is the mass 
of feeding tissue. After COULTER. 
above (figs. 528, 529). In the organization of the egg, a ventral nucleus 
is cut off, and not a ventral cell. 
Tumboa. The female gametophyte is developed as in Ephedra as 
far as wall formation ; but in the differentiation of the endosperm into 
two regions (one fourth micropylar and three fourths antipodal) there 
is very incomplete wall formation. As a consequence, the cells of the 
