EXPLANATION OF PLATES I. AND II. 405 



terminate inferiorly in ovate or irregularly oval expansions, 

 which are such as a cluster of buds situated there would 

 produce ; in only one specimen is there any appearance of 

 the branching of a spray, and in that the seeming branch 

 may be merely the impression of one twig crossing another. 

 Out of upwards of fifty impressions of twigs of this 

 Taxites, eight or ten have small round depressions on some 

 of their leaves, disposed sometimes in a pretty regular row 

 on each side of the mid-rib, but more often they are irre- 

 gular both in distribution and size. Now and then one or 

 more of the dots approaches nearer the margin of the leaf 

 than the others, sometimes they are seated on the mid- rib, 

 and occasionally one dot encroaches on another. Most of 

 the dots have a little pit in the centre, and their circum- 

 ferences more deeply impressed than the area, which is 

 often convex, though not raised above the impression of 

 the lamina. They must, therefore, have projected above 

 the surface of the leaf, whose cast is all that remains. 

 These dots bear some resemblance to the fructification of a 

 fern ; but on exhibiting the casts to Mr. Brown, he at once 

 remarked the dissimilarity of the dots to sori, in their 

 having no perceptible connection with veins, and in the 

 appearance of a membranous expansion from the epidermis 

 covering them, which his practised eye detected. On 

 examining twigs of the Canadian and common yews I 

 observed many sphacelated dots raised more or less above 

 the surface of the leaves, which would make impressions 

 very similar to those of the fossil. The dots in the recent 

 plant occur more commonly on the under surface of the 

 leaf than on the upper one, and are generally circular, 

 though sometimes irregular. They are covered by the 

 epidermis, which in the larger dots is always ruptured in 

 the centre. I have not been able to discover their precise 

 nature ; they may possibly be caused by insects, or perhaps 

 by the rupture of terebinthaceous collections. They do 

 not appear to be fungi ; and when the epidermis is removed, 

 the minute cavity is found to be lined with indurated 



