Manchester Memoirs, Vol. xlv (1901), No. 1. 13 



specimens, for such obliterated cells are very irregular in 

 their appearance^ 



So far I have been dealing with the phloem as seen in 

 the central vascular cylinder or stele of the stem. I pass 

 now to a consideration of the phloem of the leaf trace 

 bundles. These, as is well known, in passing outward 

 through the phloem region, retain on the outer surface a 

 certain amount of the tissues belonging to this region. 

 The best preserved specimen of these cells accompanying 

 the leaf trace are figured by Seward from the specimens 

 in the Binney Collection. YV\sFig. i on Plate WV? shows 

 the tissues not only well preserved but extremely thinly 

 ground. In this figure the tissue has an appearance not 

 unlike that just described for the stem of Lepidophloios 

 from Cash's specimens, and the appearance is not to 

 my mind very suggestive of a secretory tissue, but much 

 more of phloem cells. The cell walls are very distinct, 

 and there is no appearance of lysigenous degeneration 

 nor of any large amount of substance which could be 

 looked upon as secretion. The account of these cells as 

 seen in longitudinal section, and the figure he gives of 

 them Fig. 2, Plate IV., is not against their being true 

 phloem elements and concerned in conduction rather than 

 in secretion. They are at any rate very different from 

 the less well preserved tissue of the main axis, and 

 approach more closely well preserved cells of the Cash 

 specimens. 



In Cash's specimens, however, the phloem of the leaf 

 trace bundles does not present so clear an appearance as 



1 A good account of these cells (cellules nacrees) in both Phanerogams 

 and Cryptogams will be found in Perrot's Tissue crible, 1899, based chiefly 

 on the work of Jules Leger's ' Recherches sur I'origine et les transformations 

 des elements liberiens.' (ylA'w. .S"^.:. Linn. Normandie.) 



" Seward, loc. cit. Plate. 3, Fig. I. See also Binney. Trans. 

 Palaoniograph. Soc, 1872. 



