i 9 o8] BRIEFER ARTICLES 415 



The apparently simple plan of planting the seeds end down was 

 not adopted for two reasons. First, this would not give accurate 

 results, because such a seed as that of Ceratozamia could not be placed and 

 kept in an exactly vertical position, and there is no doubt that a variation 

 from the vertical of only a few degrees is sufficient to bring an organ under 

 the direct influence of gravity. Second, at the time of formation of the 

 growing points, the embryo has been pushed half-way through the massive 

 endosperm in a tortuous and winding path by the elongating suspensor, and 

 it is probable that just at the time when it comes to rest, gravity will deter- 

 mine its position whether the seed be vertical or horizontal. 



Rotation on the clinostat seems to have retarded development to a 

 marked degree, but has not otherwise interfered with it. Early in February, 

 the embryos developing on the clinostat were found to have two equal 

 cotyledons (figs. 4, 5, 6), while those developing under normal conditions 

 have only one (fig. 7). Further, the dicotyledonous embryos have a 

 tetrarch stele in the root and the cotyledonary vascular system is of the 

 usual cycad type. 



It can scarcely be doubted that gravity is the main factor in bringing 

 about the inequality reported in the cotyledons of other gymnosperms, and 

 it may be that further experiment will throw some light upon the seeming 

 suppression of root poles. It is possible also that it is to this cause we may 

 attribute not only the monocotyledonous condition long known to exist 

 in some dicotyledons, mentioned by Coulter and Chamberlain (13); 

 but even the condition of certain true monocotyledons whose embryos from 

 their very inception hold a practically unchanged one-sided relation to 

 gravity. 



The experimental work is under the direction of Professor Charles 

 R. Barnes and Dr. William Crocker.— Helen A. Dorety, The Uni- 

 versity 0) Chicago. 



LITERATURE CITED 



1. Chamberlain, C. J., Preliminary note on Ceratozamia. Bot. Gazette 43: 

 137. 1907. 



2. Van Tieghem, Ph., Symetrie de structure des plantes. Ann. Sci. Nat. Bot. 

 V. 13:204. 1873. 



3. Warming, E., Ein Paar nachtragliche Notizen iiber die Entwicklung der 

 Cycadeen. Bot. Zeit. 36:737. 1878. 



4. Matte, Henri, Note preliminaire sur des germinations des Cycadacees. 

 Rennes. 1907. 



5. Treub, M., Embryogenie von Cycas circinalis. Ann. Jard. Bot. Buit. 4:1. 

 1 88a. 



