204 BOTANICAL GAZETTE [MARCH 
Fic. 37. Cross-section of sporangium of Ceratozamia, with plate of cells 
extending from beneath line of dehiscence to the sporangial cavity. 
Fic. 38. Cross-section of mature sporangium wall; c, cell aoailicin crystals, 
just beneath the line of dehiscence; cells of inner layers of sporangial wall pro- 
jecting into outer layers; ¢, tapetum broken down; m, microspore. X 800. 
Fic. 39. Longitudinal section of two sporangia of Encephalartos. X 7o. 
Fic 40. Surface section of stoma in the sporangial wall of Encephalartos; 
g, guard cells; su, subsidiary cells. 650. 
Fic. 41. Cross-section of stoma of Encephalartos. 650. 
Fic. 42. Detail of sporangium of Ceratozamia: ¢, tapetum; sf, sporogenous 
cells. X120. 
Fic. 43. Longitudinal section of sporangium of Ceratozamia at the base; 
tapetal cells becoming more numerous by sterilization of sporogenous tissue. 
180. 
Fic. 44. First division of pollen mother cell. X 1500. 
Fic. 45. Nuclear plate in spore mother cell, showing 12 chromosomes. X 
Fic. 46. Male gametophyte of Encephalartos in 2-celled stage; p, prothallial 
cell; a, aucheridial initial. 1500 
Fic. 47. Male gametophyte of Encephalartos in 3-celled stage; p, prothallial 
cell; g, generative cell; #, tube cell. 1500. 
Fic. 48. Male gametophyte of Zamia, showing beginning of tube; lettering 
as before; 2, “third wall,” showing within intine. 1500. 
Fic. 49. Further development of pollen tube; tube nucleus passing into the 
tube; much starch present. X 1500. 
Fic. 50. Culture from Zamia, showing extrusion of tube and breaking of 
exine. 1500. 
1G. 51. Microspore of Encephalartos in resting stage. X 1500. 
Fic. 52. Microspore of Encephalartos, showing some of the chromosomes. 
The magnifications given in the foregoing explanations are those of the 
original drawings, which have been reduced three-fifths in reproduction. 
