212 THE HISTOLOGY OF THE EPHEDREyE. 



of the twigs of the accessory with the normal bud-trace before they pass to the leaves is shown (/). The 

 accessory is represented as being absent from the first two internodes of the side branch. 



Fig. 21. Diagram of the behaviour of the concrescent bundle at the end of its course, (i.) represents 

 the six bundles after the disappearance of the lateral flanges; (ii.) represents the concrescent bundle linking 

 on to the traces on either side ; (iii.) represents the concrescent bundle as split, while the non-concrescent 

 bundles have become united by the formation of intercalary tracheids ; (iv.) represents the - true vascular 

 crescents formed equally of the traces from the first node above, flanked on either side by half the con- 

 crescent bundle. 



Fig. 22. Transverse section of E. trifurca, showing fifteen bundles due to three leaves at the node, 

 each leaf-trace pair being accompanied by an accessory. x 42. 



Fig. 23. Transverse section of E. elegantissirna, showing nine bundles due to three leaves at each node, 

 the leaf-traces being concrescent in the second half of their course, x 42. 



PAPERS REFERRED TO. 



(1) Haberlandt, G., Die Lichtsinnesorgane der Laubbldtter, Leipzig, 1905. 



(2) Graham, R. J. D., " On the Light-sense Organs in Ephedrese," Trans. Scots. Mic. Soc, March 1907. 



(3) Stapf, O., "Die Gattung der Ephedreaa," Denkschr. Akad. Wissensch. Wien, 1889, Bd. lvi. 



(4) De Bary, A., Comjiartitive Anatomy of the Phanerogams and Ferns, Oxford, 1884, p. 35. 



(5) Strasburger, E., " Ueber den Bau und die Verrichtungen der Leitungsbahnen in den Pflanzen," Hist. 



Beit., 1891, Heft iii., p. 140. 



(6) Von Mohl, H., " Ueber den Bau der grossen getiipfelten Rohren von Ephedra," Linnea, 1831, Bd. iv. 



p. 593. 



(7) Strasburger, E., Die Coniferen u. die Gnetaceen, Jena, 1872, p. 115. 



(8) Dingler, H. "Ueber das Scheitelwachsthum des Gymnospermen-Stammes, " Bot. Zeit., 1882, Bd. si., 



p. 796. 



(9) De Bary, A., I.e., p. 14. 



(10) Bertrand, "Anatomie des Gnetacees et des Coniferes," Ann. d. Sc. Nat., 1874, Ser. v., Bot., torn, xx., 



p. 24. 



(11) Fritsch, F. E., "The Use of Anatomical Characters for Systematic Purposes," New. Phyt., 1903, vol. ii., 



p. 177. 



