256 BOTANICAL GAZETTE [march 



plants made 3 and 4 leaves, each i m. long and 14 cm. wide, in less 

 than a year after emerging from seed. 



Summary 



1. The cotyledons of Dioon spinulosum vary in number from 

 2 to 4, and they are often lobed and divided so as to appear greater 

 in number. In rare cases the cotyledonary sheath is undivided 

 except near the tip. 



2. They are multifascicular, like those of Ceratozamia and 

 Microcycas, rather than like those of Zamia and Cycas, which have 

 but few strands. 



3. The arrangement and orientation of the vascular strands of 

 cotyledons, hypocotyl, stem, leaves, and root do not differ in any 

 marked degree from the general cycad arrangement. 



4. The stem is large enough to demonstrate the cause of the 

 girdling habit and to bring it into alignment with certain angio- 

 sperms of the same habit. 



5. There is no extrafascicular cambium or any other vestige of 



polystyle. 



Grateful acknowledgment is due to Dr. Charles J. Chamber- 

 lain for the generous supply of material from which this study was 

 made. 



College of St. Elizabeth 

 Convent, New Jersey 



EXPLANATION OF PLATES X, XI 



The drawings 1-13 and 29 were made with the unaided eye and are 

 reduced to one-half the natural size; 14-19 are diagrammatic; the remainder 

 were made with the aid of the Abbe camera lucida. The following abbrevia- 

 tions have been used: c, cotyledon; /, leaf; s, suspensor; sc, scale leaf; si, 

 stipule; vc, vascular cylinder; x, xylem; ph, phloem; px, protoxylem; mx, 

 metaxylem; ep, inner epidermis of the cotyledons. 



Fig. I. — Ovule with young embryo and coiled suspensor. 



Fig. 2.— Seed with mature embryo, pushing out suspensor and archegonial 

 wall. 



Fig. 3. — Beginning of germination. 



Fig. 4. — Separation of cotyledonary petioles. 



Fig. 5. — Seedling germinated in vertical position. 



