28 SPERMATOGENESIS AND FECUNDATION OF ZAMIA. 
Ikeno also considers the naked nucleus expelled to be the homologue 
of the Stielzelle or stalk cell and the cell from which it was expelled 
the homologue of the Kérperzelle. It does not appear from Ikeno’s 
monograph that he observed the division of the third prothallial cell 
leading to the formation of this structure. Judging from his short 
description and indefinite figures it would seem that his material at this 
stage must have been poor or lacking. In none of his figures of the 
male prothallus does he show an interior cell like the writer’s first 
prothallial cell or strands of protoplasm such as Hirase describes in 
Ginkgo. 
The two nuclei in his ** first prothallial cell” are in position exactly the 
same as the corresponding nucleiin Zamia and Ginkgo, but no strands 
of protoplasm or cell membrane separates them. The ‘*K6érperzelle” in 
his figures 15 to 19a is indicated as entirely spherical and not influenced 
in shape at the attachment with the prothallial cell, which seems very 
unlikely. The writer is unable to suggest how this apparent differ- 
ence between Cycasand Zama can be explained. The series of Zama 
preparations on which his interpretation is based has been shown to 
several American botanists, and they entirely concur with him as to 
the structure of Zamia. 
The development of the prothallial apparatus of both Zamia and 
Ginkgo has been studied by the writer with considerable care at dif- 
ferent times during a period of nearly four years, and with abundant 
material at different stages. The interpretation given by Hirase and 
Ikeno seemed so novel and improbable that he was stimulated to a 
more thorough investigation. The early studies of Juranyi (72), ete., 
give no aid in this question, as in his study of d/acrozamia he germi- 
nated and grew the pollen on soft pieces of pear fruit, and it has been 
amply demonstrated since, that the developments obtained in this way 
were abnormal. Juranyi obtained fairly long tubes developed from 
the large pollen cell, traced the nucleus in its passage into this tube, 
and in two instances found that this nucleus had divided into two. 
The so-called Innenkérper (the prothallus), however, remained in its 
place, decreased in size as the tube elongated, and finally disappeared. 
Strasburger (110) cultivated pollen of Ceratozamia in the same way, 
and found that the Innenkoérper did not disappear as long as the tubes 
remained in apparently a normal healthy condition. Belajeff (2 and 3) 
was the first investigator to introduce the only safe method, that of 
studying the pollen tubes developed on the pistil in the normal way, 
by sections of the pistil and isolating the tubes by maceration methods. 
His study of gymnosperms, however, did not extend to any of the 
Cycadacee. 
In 1892 Strasburger described the development of the pollen and 
pollen tube of Ginkgo, but was led to erroneous conclusions, appar- 
ently, by the insufficiency of his material. He correctly described 
