1 8 Weiss, Phloem of Lcpidophloios and Lepidodendron. 



least in transverse section, does not onl\' not preclude 

 them from being of the nature of true phloem elements, 

 but makes it very probable that the function of this tissue 

 was that of a normal phloem. In both cases we have the 

 larger and smaller elements so characteristic of phloem 

 and similarly arranged, the proportion of the two kinds 

 of cells varying in the two genera, Lepidophloios having a 

 greater number of the smaller elements. 



It would be highly desirable to examine longitudinal 

 sections of equally well-preserved specimens, so as to 

 determine the suitability of the phloem elements for 

 purposes of conduction of organic material ; but we can 

 see from the less well-preserved specimens [Fig- 5) that 

 they occur in considerable vertical series, and as they are 

 often contiguous, the vertical passage might be helped on 

 by lateral diffusion. Phloem appearing in longitudinal 

 section of the normal type has been shown by Maslen^ to 

 exist in the sporophylls of Leptdostrobiis, and the trans- 

 verse sections of similar leaf traces in the excellently 

 preserved Lcpidostrobns Broivnii'- shows that in this 

 species the cells had the same arrangement as has been 

 figured by Hovelacque for Lepidodendron selagzjioides, so 

 that here, too, we might suppose that a good longitudinal 

 section might show the same arrangement as described by 

 Maslen for Lepidostrobns. 



In the vegetative axis showing secondary thickening 

 we should expect a phloem of even greater complexity, as 

 the requirements of organic food material would here be 

 greater, and, as has been often pointed out, the phloem of 

 DicotyledoJis generally develops phloem-parenchyma " for 



' Maslen, A. J. "The .Structure of Lepidostrobus. Trans. Linn. Soc. 

 Loud., Vol. v.. Pi. II., 1899. 



2 Bower, F. O., loc. cit.. Fig. 4A, PI. XVI. 

 ' c.p. Vines, S. Text-book of Botany, i8l. 



