GYMNOSPERM^. 



101 



Taxus Campbelli,^ (Taxites, Forbes). Plate X, fig. 1 ; Plate XXVII, figs. 1—3. 

 Basaltic Formation ; Ardtun Head, Isle of Mull. 



The species was described at page 41 of this memoir from the unique specimen in the 

 Museum of Practical Geology in Jermyn Street, as Sequoia Layigsdorfii, Brong. ; the figure 

 (PI. X, fig. 1) seemed to justify, or at least not to contradict, the universally accepted view- 

 promulgated by Heer as to its generic affinity with Sequoia. My personal researches in 

 the Ardtun leaf-beds in the present year have, however, shown me that this accepted view 

 is erroneous, and have upheld the correctness of Brongniart's and Edward Forbes's original 

 determination. In justice to these most able observers, I embrace the opportunity of 

 withdrawing a correction, which I am now convinced was unjustifiable, linger, Weber, 

 Goeppert, and others had repeatedly described twigs with similar foliage under the name 

 Taxites, believing them to belong to the Yew or the Yew tribe ; and nothing is more 

 remarkable than the way in which authors permitted every yew-like twig of Tertiary 

 age to be swept into the genus Sequoia, when we examine the evidence upon which the 

 change in the nomenclature was based. ^ 



There are many peculiarities in the Ardtun Conifer which are not met with in the 

 Redwood, but are characteristic of the Yew, though they are perfectly indistinguishable, in 

 either the fossil or recent state, by the actual form of the leaflets. Foremost among these is 

 the fact that the foliage of the Redwood, shed in summer and autumn, breaks up and falls 

 in the vast majority of cases as simple, unbranched twigs, many of which are very long, 

 and comprise two or three years' growth. The Yew behaves quite differently, the 

 majority of the twigs shed remaining compound. The specimens figured, as well as 

 others, suffice to show that the fossil species by no means broke up in the manner of the 

 Redwood, but distinctly after that of the Yew. Another character which can be detected 

 in very few fossils, the stem being generally a more or less indistinct coaly mass, is the 

 insertion of the leaves. In Taxus the base is constricted, almost petiolate, where it 

 approaches the stem, swelling out again into a sort of cushion where it is adnate or 

 embraces the stem ; ^ while in Sequoia the constriction is more apparent than real, being 

 chiefly due to the sharpness of the twist made by the leaf in becoming decurrent to the 

 stem, and there is never any sort of thickening. In consequence of this the leaves are 

 comparatively readily detached in the Yew, and most persistent in the Redwood. 



^ See Sequoia Langsdorjii, p. 41, for history and description. 



2 For many years all the yew-like foliage of the Tertiaries was determined as Sequoia Langsdorjii, 

 and its presence, as in Mull, went far in giving the age of the beds as Miocene. 



^ The leaves clothing the branchlets, which are destined to remain attached for a long time on the 

 Yew, become more and more constricted with age at the point of contact with the stem, until at last they 

 become distinctly articulated and fall off, leaving the stem clothed with the scale-like bases of the leaves 

 only. This never happens in Sequoia, where the whole leaf remains attached as a spiny scale until it 

 decays away. 



