1922] BENSON—HETEROTHECA GRIEVII I4I 
LITERATURE CITED 
coal 
. 
ARBER, E. A. N., On a new pteridosperm possessing the Sphenopteris 
type of foliage. Ann. Botany 22:57-62. pl. 7. 1908. 
2. ————. Devonian floras. Cambridge Univ. Press, p. 61. fig. 34. 
. BENSON, MARGARET, Contributions to the embryology of the foe 
Part I. Trans. Linn. Soc. London 3:412. figs. 7. 1894. 
w 
4. , Telangium Scott. Ann. Botany 18:161-177. 1904. 
5. ———,, Sphaerostoma ovale. ‘Trans. Roy. Soc. Edinburgh 50:1-15. 1914. 
6. , Mazocarpon. Ann. Botany 32: 586. 1918. 
7. CouLTER, J. M., and Lanp, W. J. G., Torreya. Bor. Gaz. 39:163. 1905. 
8. Gorpon, W. T., On the nature and occurrence of the plant-bearing rocks 
at Pettycur, Fifeshire, Scotland. Trans. Geol. Soc. Edinburgh 9: 1909. 
9. Kinston, R., the microsporangia of the Pteridospermeae. Trans. 
Roy. Soc. London, Series B. 198: 428. 1906. 
to. Kipston, R., and Lane, W. H., a = sandstone plants. Part IV. 
Trans. Roy. Sac. Edinburgh 52 :Bc2 
11. Natuorst, A. G., Paleobotanische “srictdindge. Handl. Kgl. Svensk. 
Vetensk.-Akad. 43:1-12. figs. 3. 1908. 
12. OLIVER, F. W., Structure and afinities of Slephanospermum. Trans. Linn. 
Soc. London 6: 361-400. 1904. 
, On Physostoma duels Williamson, an archaic type of seed from 
the Palsceile rocks. Ann. Botany 23:103. 1909. 
14. SALISBURY, E., Trigonocarpus Shorensis. Ann. Botany 28:74. 1914. 
15. SELLARDS, E. H., Notes on the spore-bearing organ Codonotheca, and 
its relationship with the Cycadofilices. New Phytol. 6:175-178. 1907. 
16. Starr, A. M., The microsporophylls of Ginkgo. Bor. Gaz. 49:53. I910. 
17. TREUB, M., Sur les Casuarinées. Ann. Jard. Bot. Buitenzorg 10:172. 
1891. 
EXPLANATION OF PLATES IV AND V 
The following abbreviations are used in the illustrations: 6, buttress or 
interstitial tissue between peripheral loculi; ¢, epidermis; g, gap in stone 
section; gt, ground tissue; /, loculus; cl, central loculus, me, nerve ending; 
res; sp, sclerotic plate; i plate attached to loculus wall; vsp, vertical 
sees plate; vb, vascular bun 
PLATE IV 
Fics. 1, 2.—TIwo successive cross-sections of immature synangium; 
epidermis is preserved, and in center of body occur small sclerotic plates; 
no central loculi can be distinguished, and content of peripherous ones is 
amorphous; matrix has been left around fig. 1 (CN .386.11,12); X33 diameters. 
Fics. 3, 4.—TIwo successive cross-sections of synangium nearer base; 
central loculi well shown (CN.383.12, 13); X29 diameters. 
