Professor Dyer — On some Eocene Fossil Wood. 243 



in the fossil, but capsules filled with green matter in the recent 

 plant." (p. 22.) 



Many instances of Tylose are now known amongst recent plants, 

 and have been repeatedly made the subject of investigation by 

 foreign writers, Malpighi, indeed, in his "Anatome Plantarum,"^ 

 gives a very fair representation of them in the oak (tab. 6), remark- 

 ing (p. 9), "fistulse frequenter pitZmoreares quasi vesiciilas trachearum 

 substantia excitatas continent." Without going into the literature of 

 the subject, which is considerable, it is sufficient to state that the in- 

 vestigations of an anonymous writer in the Botan. Zeit. for 1845,' 

 confirmed by MohP and Eeess (Bat. Zeit., 1868), appear to leave little 

 doubt that the "Thy lien," as the first- mentioned writer named them, 

 are hernioid protrusions into the vessel from adjacent cells. In the 

 words of Eeess, "each young Thylle makes its appearance as a 

 bulging of a wood-parenchymatous or medullary-ray cell forced 

 through a pore in the vessels." This process would be inconceivable 

 in the case of the prosenchymatous cells ; but parenchymatous cells, 

 such as those mentioned above, which surround the ducts, and those 

 which form the medullary rays, do not undergo the same amount of 

 speedy induration. In Figs. 5 and 6 transverse and longitudinal 

 sections are given of the wood of the vine, showing that the 

 "Thyllen" are precisely comparable in this and in the Eocene wood 

 (Figs. 1 and 2). Mr. Sorby has also figured in the third vol. of the 

 Mic. Soc. Trans, (pp. 91-92) a " non-gymnospermous exogenous 

 wood" from the Lias near Bristol, which shows evident traces of 

 Tylose. 



Fig. 4 represents a portion of the wall of the ducts from the 

 Thanet wood, to show the arrangement and character of the pores. 

 These are, as is well known, formed by intermissions in the internal 

 thickening which the walls of the ducts (as of other cells) undergo. 

 They are therefore closed externally by the primary membrane of 

 the duct, and this must, therefore, undergo rupture or resoi'ption 

 before the Thyllen can be developed. The pattern of these pores is 

 peculiar, but not uncommon. Dr. Bowerbank founded upon them an 

 affinity of the London Clay wood to the genus Piper. Similar pores, 

 are, however, figured by Sachs, in the widely remote Dahlia. 



Prof Van Heurck, of Antwerp, has used the term Tylose for the 

 structure termed by German writers " Thyllen." * I think, as the 

 former word will anglicize more conveniently than the latter, we 

 may follow his example. 



*^* Fig. 4 is magnified about 250, the rest about 120 diams, 



1 1686, vol. i. 



* Prof. Van Heurck, informs me that this paper, signed "von einem Ungenannten," 

 was written by Mdlle. la baronne Hermine von Reichenbach. See, for an abstract, 

 Ray Soc. Rep., 1849, p. 237. 



* See Ray Soc. Rep., 1849, pp. 26, 27. Mohl found Tylose in Palms ; the structure 

 is therefore not peculiar to Dicotyledons. 



* Sachs, Lehrbuchd. Bot., 1870, p. 27, calls them TuUen. 



