276 MINNESOTA BOTANICAL STUDIES 



tinct where they are in contact. The plumule is very conspic- 

 uous between the elongated cotyledons, three or more leaves 

 appearing just behind the stem apex." 



In 1872 Strasburger published the first paper dealing with the 

 embryogeny of Ginkgo. He determined the general course of 

 events in the formation of the spherical embryo but insufficient 

 material prevented the working out of details. Hirase ('95) 

 studied fecundation and the origin of the spherical embryo. He 

 found that there were eight simultaneous nuclear divisions in the 

 oosperm preceding free-cell-formation. More recently Ikeno 

 (1901) has made a very careful study ot the process of 

 fecundation. 



The embryo of the seed has been frequently described, but 

 little however seems to be known of its histology. Endlicher 

 ('47) was the first to mention the occurrence of two or more 

 embryos in one seed and recently Cook (1902, 1903) has called 

 attention to polyembryony in Ginkgo. Miss Wigglesworth 

 (1903) notes the presence of stomata on the cotyledons. 

 LeMaout and Descaisne ('76) and Masters ('91) figure seedlings 

 of Ginkgo. Van Tieghem ('70, '87) and Van Tieghem and 

 Douliot ('88) record observations on the anatomy of the root 

 system. Worsdell ('97) describes the vascular bundle and trans- 

 fusion tissue of the cotyledon, and Seward and Gowan (1900) 

 contribute some further observations on the anatomy of the 

 seedling. 



The remarkable ciliated spermatozoids of Ginkgo have 

 received such critical attention from Japanese botanists l that no 

 observations on these need be offered here. . With the corrobo- 

 rative evidence from the cycads z our knowledge of the occur- 

 rence and development of ciliated spermatozoids in these Gym- 

 nosperms may be considered well established. In the present 

 paper the subjects of oogenesis, spermatogenesis and fecunda- 

 tion will be avoided, the recorded observations dealing solely 

 with the embryogeny. It is purposed to take up and continue the 

 subject where Strasburger left it some thirty years ago. 



MATERIAL. 



The investigations, which are recorded in the following pages, 

 were begun in 1901 on material received from the Botanical 



'Hirase ('96, '97, '98), Fujii ('98, '99), Miyake ('98, 1902). 



2 Ikeno('96, '97), Ikeno and Hirase ('97), Webber ('971, '972, 1901), Lang (1900). 



