,8^. AMBER AND FOSSIL PLANTS. 379 



many cases, where the resin has acted as an agent of petrifaction, 

 we have plant-tissues preserved in wonderful perfection, sometimes 

 rendering visible even nuclei in delicate parenchymatous cells, and 

 giving us an insight into the minute anatomical structure of these 

 Tertiary fossil plants, even more complete than that presented by the 

 silicified Palaeozoic plants of Grand Croix and Chemnitz, or the 

 calcified remains in our English Coal-measures. In the form of an 

 incrustation, Amber has no less distinctly preserved fragments of 

 twigs, leaves, buds, and flowers ; waifs and strays of Tertiary floras 

 caught up in the slowly flowing resin or blown by wind and carried 

 by animals on to the surface of the sticky exudations of resinous 

 tissues. 



The Amber which has rendered possible these microscopical 

 examinations of fragments of a former vegetation, was present in the 

 form of resin in ducts and receptacles scattered through the cortical 

 and woody tissues of Conifers. In living trees, such as Pinus and 

 many other Conifers, resinous secretions occur in lysigenous and 

 schizogenous spaces ; spaces, that is, due either to the absorption of 

 groups of cells or to the gradual separation of uninjured cells. Resin 

 is present, both as a normal product of the vital activity of healthy 

 plants, and, in still greater abundance, as the result of wounds or 

 injuries of various kinds which stimulate the secreting cells to abnormal 

 activity and an increased production of resin. This abnormal occur- 

 rence of resin in living trees has been called by Frank Resinosis ; for 

 a similar phenomenon in the " Amber trees " Conwentz (2) proposes 

 the term Succinosis. 



Not only has the Amber been furnished by resins in horizontal 

 and vertical ducts and spaces scattered through cortex, wood, 

 medullary rays, and pith, but occasionally the well-preserved sections 

 of Amber trees have revealed the existence of special groups of 

 parenchymatous cells in the middle of woody tissues, and which have 

 been set apart for resinous secretions. Occasionally, too, succinosis 

 is seen in old tracheids of the wood whose membranes and cavities 

 have become filled with resin, or in an unusually large number of 

 schizogenous spaces in various parts of stems ; the result of 

 injurious atmospheric or organic influences which have made extra 

 demands upon the resin supplies. If we picture to ourselves the 

 thick Eocene forests in which animal and plant life was luxuriant and 

 Nature worked with a free hand, it is not surprising to find that 

 resinous material was produced on a larger scale than in the Pine 

 woods of modern Europe where the forester's art and the altered 

 climate have lessened the severity of the struggle for existence. 



Dr. Conwentz, of Dantzig, whose recent monograph gives us full 

 descriptions of the coniferous trees^ the minute anatomical structure 

 of which has been so clearly preserved by the resinous impregnations, 

 prepared himself for the task of reading the Amber records by a 

 careful study of the conditions of forest-life to-day, especially in 



