TATESIA. 165 



Genus YATESIA, Carruthers. 

 [Trans. Linn. Soc. vol. xxvi. 1870, p. 687.] 



This generic name was proposed by Carruthers for a form of 

 cycadean stem originally described as Cycadeoidea Tatesii, Carr. 1 

 The genus is thus defined : 



" Trunk cylindrical, of uniform thickness, and covered with 

 the short persistent bases of the petioles ; scars of the aborted 

 leaves scattered among those of the true leaves. Andrcecium 

 unknown ; gynoacium forming a cone, each carpophyll of which 

 bears two reflexed ovules." 



The characters of the floral structures are based on certain 

 cones of somewhat doubtful affinity, which have not been found 

 in actual connection with Yatesia stems, and cannot, therefore, 

 be regarded as of much value. In some of the specimens referred 

 to this genus, the general arrangement of the tissues, and to 

 some extent the histological structure, have been preserved, but 

 the latter are but very imperfectly known. If we examine the 

 figures of stems included in Yatesia, we shall find it a difficult 

 task to distinguish some of the examples figured by Carruthers 

 from stems referred to the genus Bucklandia. The form of the 

 leaf-scars in Suclclandia Miller iana, Carr., 2 agrees closely with 

 that in the Yatesia stems ; and in Y. Joassiana, Carr., 3 there 

 appear to be distinct indications of the transverse constrictions 

 in the stem, as in many bucklandian stems ; the form of the 

 leaf bases is also very similar in the two genera. Questions as to 

 differences in age, stages of growth, and the manner of preservation 

 of the stems, render the discrimination and exact limitation of 

 generic types exceedingly difficult, or even impossible ; my im- 

 pression is, that at all events in some of Carruthers' species there 

 are no satisfactory grounds for the application of two generic 

 names. It does not seem possible to draw any distinct line of 



1 Carruthers (6). 



2 Carruthers (1), pi. Iv. fig. 1. 



3 Ibid. pi. Iv. fig. 8. 



