OF LOWER GREENSAffD PLANTS. 255 



. So far as I can ascertain, no fossil in the least 

 like the above has yet been described. Were the tissues proved 

 to be wood, they would represent a striking new type of organi- 

 sation, which would tempt one to look upon it as a " Pro- 

 Angiosperm," intermediate between a higher Gymnosperm and 

 an Angiosperm. Its external appearance is entirely wood-like, 

 while the microscope reveals the uniform presence of entirely 

 uniseriate medullary rays, a feature unparalleled in any tissue 

 of the thickness of the present fossil, except wood, so far as my 

 experience goes. Further, the strongly marked, circular pits of 

 the pitted elements are very tracheid-like superficially, though 

 this is probably due to the nature of the petrifaction. 



Nevertheless, were the tissues present in but a small quantity, 

 there is no doubt that the regular alternation of fibres and 

 thinner-walled elements would lead to its identification as 

 phloem. A good account of the phloems of many Gymnosperms 

 and Angiosperms is to be found in Moeller (1882), to which 

 reference should be made. I am indebted to Mr. A. J. Wilmott 

 and Mr. W. N. Edwards, of the Museum, for drawing my 

 attention to this very useful book. 



As is well known, in Cryptomeria, Phyllocladus, Thuja, and 

 other Gymnosperms, the phloems show a regular alternation 

 between fibres and soft cells, differing in the numerical pro- 

 portions of the cells, but otherwise very similar to the fossil. 

 In general, the true phloem has a maximum thickness of 

 3-4 mm., and even in the giant Sequoia a trunk in the 

 Museum with a girth of over 40 ft. has a narrow zone of phloem 

 averaging only about 4 mm. thick ; outside this the corky tissues 

 are quite broken up and irregular. Mr. Boodle, however, tells 

 me that he has cut a Taccodium phloem 12 mm. thick. 



The fossil, therefore, must have been a giant phloem if it is 

 a phloem, as appears to me to be the case. Assuming that this 

 is its nature, it has two peculiar features worthy of remark. 

 First, its immense size: this must have resulted from the 

 holding together instead of the exfoliation of the successive 

 zones cut off by the unusually regular series of narrow corks. 

 Were the thickness of the phloem less, the presence of uniseriate 

 rays would not be remarkable, because such are found in the 

 narrow phloems of several Gymnosperms. Second, the position 

 and character of the parenchyma-cells. In the living Thuja, 



