288 MINNESOTA BOTANICAL STUDIES. 



Wiggles worth, Miss Grace. 1903. The cotyledons of Ginkgo biloba 

 and Cycas revoluta. Ann. of Bot., 17: 789-791. 



Worsdell, W. C. '97. On " Transfusion-tissue " its origin and func- 

 tion in the leaves of gymnospermous plants. Trans. Linn. Soc., 

 5: 301-319. 



DESCRIPTION OF PLATES. 

 Plates 3^, 36, 37 and 39 are after photographs by Mr. C. J. Hibbard. 



PLATE 29. 



1. Sectional view of a protocorm in which free-nuclear-division 

 has ceased. From a section 20 thick ( x 160). 



2. Section of protocorm just after completion of free-cell-formation. 

 Section 10 thick (x 160). 



3. Surface view of a protocorm (x 160). 



4. Section of a protocorm in the basal portion of which a blastema 

 is being organized (x 160). 



The outlines for figs, i, 2 and 4 were traced from photomicrographs. 



PLATE 30. 



5. Longitudinal section of a young embryo in which the position 

 of the root-apex is just distinguishable (x 130). 



PLATE 31. 



6. A similar section of an older embryo showing first indication 

 of cotyledon-primordia (x 130). 



PLATE 32. 



7. Shows relation of metacorm to protocorm. The cotyledons 

 are well advanced and secretory canals are appearing in both plerome 

 and periblem (x 57). 



PLATE 33. 



8. From a section of a gametophyte containing a young embryo 

 (X 39). To the right can be seen the empty venter of the second 

 archegonium. Disorganization of the tissue of the gametophyte is 

 evident for some distance ahead of the embryo. 



9. An instance where two blastemata were organized in one proto- 

 corm, but only one developed into a metacorm (x 36). 



10. Section of a young embryo in a plane parallel to the faces of 

 the cotyledons, passing through the stem-apex and primordia of the 

 first two plumular leaves (x 57). 



11. 12. Two sections of mature embryos cut, the one parallel, the 

 T perpendicular to the plane of contact of the cotyledons ( x 12). 



These sections show, in a general way, the relation of parts, differ- 



