THE STRUCTURE OF THE STOMATA OF CERTAIN 



CRETACEOUS CONIFERS 1 



W. P. Thompson 



(WITH PLATES V AND Vl) 



The structure of the stoma is remarkably uniform in all members 

 the plant kingdom, from Anthoceros to the highest angiosperms. 

 consists essentially of an aperture surrounded by two guard 

 tfhich may be more or less sunken and protected by adjacent 



cells. 



from 



more 



for the fossil genus Frenelopsis, first by Zeiller, 2 and 

 by Berry. 3 These authors state that in place of th>e usual two 

 guard cells, each stoma of Frenelopsis is surrounded by four or 

 five guard cells in the form of a rosette. The uniqueness of this 

 supposed condition made it desirable that the subject should be 



■ m 



reinvestigated, and for this purpose I have had access to material 



of Frenelopsis occidentalis (Heer), supplied by Professor Zeiller 



from a collection made at Nazareth, Portugal, by Professor 

 Choffat. 



The characters of the genus Frenelopsis have been given in 

 detail by Ettingshausen, 4 Schenk, 5 and others. It is a cretaceous 

 conifer of disputed affinities, being referred by some authors 

 to the Cupressineae and by others to the Gnetales. The leaves 

 are decussately arranged in twos or fours at the nodes of the jointed 

 stem. They are reduced, squamiform, and appressed. The inter- 

 nodes functioned as leaves. 



The epidermal characters of Frenelopsis occidentalis have been 



x Contributions from the Phanerogamic Laboratory of Harvard University* 

 No. 45. 



2 Zeiller, R., Observations sur quelques cuticules fossiles. Ann. Sci. Nat. Bot. 

 6: i3- 1882. 



3 Berry, E. W., The epidermal characters of Frenelopsis ramosissima. Bot. 

 Ga * 50:305-309. figs 2. 1910. 



4 Ettingshausen, C, Abhand. k.k. geol. Reichsanstalt. Vol. I. 



5 Schenk, H., Palaeontogr. 19:13. — . 



63 



[Botanical Gazette, vol. 54 



