Lyon: THE EMBRYOGENY OF GINKGO. 277 



Gardens of the Imperial University of Tokyo through the kind- 

 ness of Mr. K. Yendo. Later large quantities of excellent 

 material were obtained from the Missouri Botanical Garden, 

 and it is principally from this material that embryological data 

 have been obtained. The writer wishes to express his sincere 

 thanks to Dr. William Trelease who has done every thing pos- 

 sible to facilitate the work. Some valuable preparations have 

 also been obtained from a small number of seeds purchased from 

 Thorburn & Co., seed dealers of New York. The location of 

 the trees which bore these seeds was not determined. The 

 material sent from Japan by Mr. Yendo, amounted to several 

 quarts of seeds containing nearly mature embryos. The embryos 

 were removed from a large number for examination, those 

 shown in Plate XXXV. being some of the number, while many 

 of the seedlings studied were grown from these seeds. Under 

 the directions of Dr. Trelease, cuttings bearing megasporangia 

 were sent from the Missouri Botanical Garden at intervals of a 

 few days throughout an entire season. After the cut ends of 

 the branches had been sealed over with paraffin, they were 

 packed in moist sphagnum, wrapped first with oiled, then with 

 heavy paper and sent by parcel-post. These excellent precau- 

 tions brought the material to this laboratory in a perfectly fresh 

 condition. Upon arrival it was immediately placed in the 

 various fixing fluids. 



RESEARCH. 



A. The Embryo. 



i. The Protocorm. At the completion of free-division the 

 nuclei are quite evenly distributed through the cytoplasm of the 

 oosperm (Jig. /), and when the formation of walls between 

 these nuclei is first completed the resulting cells show no marked 

 dissimilarity in shape, size or contents (fig. 2). The cells, in 

 the upper two thirds or more of this spherical protocorm, divide 

 only a few times or not at all. Their protoplasmic contents be- 

 come thin and watery, and they take no part in the organiza- 

 tion of the metacormal bud or blastema. The cells in the lower 

 portion of the protocorm divide repeatedly, the relative activity 

 increasing towards the base so that in this region there is organ- 

 ized a small-celled tissue (figs. 3, 4). This basal tissue passes 

 over directly into the small-celled meristem of the blastema. 

 With the advance of the metacorm into the body of the gameto- 

 phyte, the protocormal tissue is forced back through the neck 



