332 ON THE MOEPHOLOGT OF THE GEJS"US GNETUM. 



Fig. 3- Tangential longitudinal section tLrongli the same ovule. N=uucellus; b= bud in axil of 



outer integument, x 300. 



Fig. 4. Part of a longitudinal section through the node of the pseudo-androgynous spike^ showing an 



incomplete female flower, two male flowers, and undifferentiated mcristem (M). N 

 nucellus -, O = outer, I = inner^ ?n = ? middle envelopes of ovule ; ^ = male flower; 

 p= perianth of male flower, x 300. 



Fig. 5. Longitudinal section of an incomplete female flower, slightly older than that of fig. 4. 



O = outer, I = inner, m^t middle envelopes. X 300. 



Fig. 6. Longitudinal section of a male flower bearing four anthers. P= perianth, x 70. 



Fig. 7, Longitudinal section of a very young male flower. The primordia of the two anthers are 



indicated. P = ring-like perianth. X 300. 



Fig. 8. A four-chambered microspore mother-cell. X 1200. 



Fig. 9. Two pollen-grains from the micropyle of a complete flower of an androgynous spike. X 1200. 

 Fig. 10. A longitudinal section through an embryo-sac of G. 



longitudinal section through an embryo-sac of G. africanum i 

 The nuclei at the chalazal end of the sac are crowded, x 300. 



Fig. 11. Top micropylar end of the same sac as fig. 12^ showing free gamete-nuclei. 



Fig. 12. The chalazal end of a later stage of the embryo-sac^ showing septation into multinucleate 



compartments, x 700. 



Fig. 13. The chalazal end of an embryo-sac wdth the underlying nucellar tissue, showing an early stage 



in the formation of ^' pavement tissue ^' (jp-t.^. 

 Fig. 14. Gamete-nuclei from the micropylar half of an embryo-sac. 



Plate 32. 



Fig. 15. Three cells from the chalazal end of the same sac as in fig. 14, showing stages in nuclear 



fusion. X 1200. 

 Free gamete-nuclei from the micropylar half of a sac. 



Cells from the upper part of the lower half of the same sac^ showing an advanced stage in 

 nuclear fusion, the nucleoli being still unfused. x 1200. 



Outline of a more advanced embryo-sac, showing approximately the division into sterile {b) and 

 fertile [c) regions, x 70. 



The lower part of the endosperm-tissue of the sac of fig. 18, with a part of the underlying 



nucellar pavement tissue. In most of the endosperm cells nuclear fusion is proceeding or 



completed ; in a few the nuclei are still free. 

 The upper part of the micropylar region of the same sac, showing the irregularly distributed 



free gamete-nuclei- 

 Longitudinal section through micropylar half of a more advanced embryo-sac, showing fertile 



region with free gamete-nuclei and its junction with the top of the primary endosperm. 

 Chalazal end of the same sac, showing almost the whole of the primary endosperm. Except in 



a few cells, nuclear fusion is complete, x 300. 



The pollen-tube has traversed the greater part of the length of the nucellar cap, but has 



Fig. 



16 



Fig- 



17 



Fig. 



18 



Fi«- 



10 



Fio- 



20 



Fig. 



21 



Fig. 



22 



bry 



Fig. 23 



more 



of the primary endosperm cells, showing the very different sizes of the constituent cells 

 (cf. WelwitscMa, Pearson, 1909, fig. 88). x 300. 



