﻿3 6o 



BOTANICAL GAZETTE 



to the transfer from one hemisphere to another, for Stangeria in the 

 Botanic Garden at Sydney was shedding in December 191 1. 

 The pollen at the time of shedding shows a prothallial cell, a genera- 

 tive cell, and a tube cell, a condition which I have now observed 

 in all the 9 genera of the family. 



Early stages in the development of the pollen tube were not 

 observed, but later stages indicate that they do not differ essentially 

 from the course already described in detail for Dioon edule (n). 

 A characteristic view of the pollen tube structures after the pollen 

 chamber has extended entirely through the nucellus is shown in 

 fig. 2. In the tube at the right the body cell has divided, but in 

 the rest the division has not yet taken place. The tube nucleus 

 is regularly near the body cell. The haustorial end of the tube 

 extends in a straight line a few layers of cells below the epidermis, 

 scarcely ever showing any branching, and there are no basal 

 haustoria like those of Ceratozamia. While the pollen tube struc- 

 tures of the cycads present many similarities, the differences are 

 probably sufficient for a determination of the genera. 



By comparing figs. 2 and 3, which are drawn to the same scale, 

 it is evident that in the later development both the tubes and the 

 sperms increase greatly in size. It is during this rapid increase in 

 size that the spiral band with its immense number of cilia develops 

 from the blepharoplast. The cycad sperm is the largest and most 

 complicated motile cell in either plants or animals. While the 

 series of stages in Stangeria is quite satisfactory, the series in Cera- 

 tozamia is even more complete, thanks to Mr. Alexander M. Gaw, 

 of Jalapa, Mexico, who for 10 years has been sending material to 

 supplement my own collections. Besides, the blepharoplast of 

 Ceratozamia is larger. Consequently, a more detailed study of 

 the development of the sperm will be reserved for this genus; but 

 some of the more obvious features, as they appear in Stangeria, 

 will be presented here. 



While the body cell remains elongated during the early stages 

 in the development of the tube, the two blepharoplasts occupy the 

 fore and aft positions; but as the basal end of the tube enlarges and 

 the body cell becomes spherical, the blepharoplasts rotate 90 , so 

 that their axis becomes transverse to the long axis of the tube. 



