THE ANATOMY OF THE STEM OF THE PAPAVERACE^. 607 



composing it may fuse laterally just before their insertion on the vascular ring into 

 two or four vascular cords. In other cases the vascular bundles remain isolated 

 throughout. Again, the vascular tissue of the axillary branch may be inserted half 

 on either side of the leaf-trace or may be partly or wholly intercalated between the 

 leaf-trace strands. 



4. Laticiferous tissue occurs in all the Papaveracese examined, but its distribution 

 and histological differentiation vary in different cases. There is a gradual transition 

 from the simple laticiferous tissue of Corydalis, where it occurs chiefly in the non- 

 vascular areas, to the complex system seen in Papaver and Argemone, where it 

 occurs exclusively in the vascular system. Meconopsis and Chelidonium form 

 transitional types, for their laticiferous tissue is found at the periphery of the 

 vascular bundles and consists of articulate tubes which are seldom branched. 



The discussion of the exact affinities of the different genera must of necessity be 

 postponed until the anatomy of the other organs has been investigated. 



BIBLIOGRAPHY. 



(1) Elkan, Tentamen mow/graphix generis Papaver. Kbnigsberg, 1839. 



(2) Hill, "Histology of the Sieve Tubes of Angiosperms." Annals of Botany, xxii, 1908. 



(3) Van Tieghem, " Un nouvel exemple de tissue plisse." Journal de Botanique, t. v, 1891. 



(4) Link, Icones Anatomico-Botanicx. Berol, 1837-42. 



(5) Solereder, Systematic Anatomy of the Dicotyledons. Oxford, 1908. 



(6) De Bary, Comparative Anatomy of Phanerogams and Ferns. Oxford, 1884. 



(7) Sanio, Botanische Zeitung. 1864. 



(8) Engler and Prantl, Die natilrlichen Pfianzenfamilien. Yol. iii, 1891. 



(9) Leger, "Les laticiferes de Glaucium et de quelques autres Papaveracees." Bull. Soc. Linn. Normandie, 



ser. 4, vol. v, 1891. 



(10) Leger, "Recherches sur Pappareil vegetatif des Papaveracees." hoc. cit., vol. xviii, 1895. 



(11) Legbr, "Sur la presence des laticiferes chez les Furnariacees." Compt. Rend. Acad. Sci., cxi, 1890. 



(12) Moebius, Ber. deut. hot. Gesell. 1887. 



(13) Sarton, "Rech. exp. sur l'anatomie des pi. affines." Ann. Sci. Naturelles : Bot., ser. 9, t. ii, 1905. 



(14) Junge, "Beitrage zur Kenntnis des Gefasspflanzen Schleswig-Holsteins." Jahrb. Hamb. wiss. Anst., 



xxii, 1904. 



(15) Eastwood, Proc. Calif. Acad., ser. 3, Bot. 1. 



EXPLANATION OF PLATES. 



(All figures marked " L " are drawn under a magnification of approximately 80, those marked "H" 

 under a magnification of 450, save where otherwise stated.) 



Plate I. 



Fig. 1. Transverse section of stem of Papaver Bhosas (L). 

 „ 2. Transverse section of the peripheral region of the stem (H). 

 „ 3. Longitudinal section of the stem, showing sieve plates and sieve fields ( x 800). 



