﻿194 BOTANICAL GAZETTE ' [march 



EXPLANATION. OF PLATES VI-VIIL 



AH the figures are from Zamia floridana. Figs, ij~i6 are from photo- 

 micrographs of rather thick sections. The rest of the figures, except 7?^^, J> 

 //, 12^ are from camera lucida drawings. 



Fig. I, The mitotic figure which gives rise to the nuclei of the egg and 

 the ventral canal cell. X 200. 



Fig, 2. A later stage showing the two neck cells (a), the ventral canal 

 nucleus {v), and the nucleus of the e^gg {e). X 45. 



Fig. 3. Upper portion of the gametophyte showing two archegonia; the 

 nucleus of the fertilized ^g^ {ft) is plainly visible to the naked eye. Nat- 

 ural size. 



Fig. 4, Free simultaneous nuclear division in the proembryo ; the num- 

 ber of mitotic figures in this proembryo is estimated at 128; the two large 

 irregular nuclei at the top may have come from a male cell; the spindle- 

 shaped bodies at the top are probably coagulated food material. X 25. 



FiG. 5. Proembryo after simultaneous free nuclear division has ceased; 

 the remains of the blepharoplast (^) can still be seen. X 20. 



Fig. 6. A stage slightly later than that shown in Ji£. 3 ; the strands at 

 the bottom seem to be related to the settling of the nuclei. X20. 



Fig, 7. The beginning of wall-formation at the base of the proembryo. 

 X 20. 



Fig. 8. Differentiation into suspensor and embryo proper becoming dis- 

 tinguishable. X 30- 



Fig. g. A more advanced stage, the embryo and suspensor being quite 

 definitely outlined ; the faint and incomplete septation above the suspensor is 

 also shown. X50. 



Fig. 10, A still later stage; the suspensor has lengthened considerably ; 

 no central vacuole has yet been formed, although the cytoplasm in the region 

 occupied by the vacuole in Cycas at this stage and earlier is becoming 

 scanty. X 36. 



Fig, 11. Young embryo dissected out from the seed; the suspensor has 

 been pulled out straight. Natural size. 



Fig, 12. a nearly mature embryo, showing the two cotyledons and sus- 

 pensor. Natural size, 



i 



Fig. 13. Upper part of gametophyte showing embryo and characteristic 

 cavity formed by disintegration of surrounding tissues. X I4- 



Fig. 14. Three embryos in about the same stage as that shown in the 

 preceding figure. X45. 



Fig. 15. Tip of young embryo pressing into the endosperm. X 185. 



Fig. 16. Young embryo with a portion of the suspensor. X 140. 



