6 Weiss, Phloem of LepidopJiloios and Lepidodendron. 



to. It would, of course, be quite possible for the divisions 

 to stop at this stage so that we should not obtain a 

 definite central cell. There were, however, other groups 

 of cells showing the same state of things as in the group 

 in Fig. 4, but a little less clearly. The number of cells 

 was not alwa}\s the same. Sometimes as few as four 

 were noted, and then, usually, no central cell occurred. 

 Generally, however, they were more numerous, and in a 

 specimen of LepidopJdoios I have just received from my 

 friend, Mr. William Cash, in which there are a great 

 number of these divided large cells, the number of 

 divisions is often very great, both the central and the 

 peripheral cells having divided up into smaller cells. 

 Indeed, the whole of the phloem region seems to have an 

 active meristematic condition and to be undergoing con- 

 siderable change, and the tissues have thereby become so 

 irregular that they differ a good deal from the prepara- 

 tions figured in this paper. As the secondary thickening 

 is only just commencing in the preparation lent me by 

 Mr. Cash, it must be considered as younger in age than 

 in the specimens from the Manchester Museum in which 

 such division stages are much less numerous and the 

 star-shaped arrangement more common. The increased 

 number of groups of cells of this latter category in the 

 older specimen suggests that after the subdivision of the 

 cells the star-shaped appearance has been produced by an 

 enlargement of the central cell and by further growth of 

 the peripheral cells of a subdivided phloem cell, such as is 

 figured in Fig. 4. 



These star-shaped groups resemble very closely the 

 sieve tubes, surrounded by small parenchymatous cells, as 

 described and figured by Hovelacque' for Lepidodendron 



^ Hovelacque. " Recherches sur le Lepidodendron selaginoides." 

 Mem. Soc. Linn. Normandie, .\vii'"« Vol., i"fas., 1892, pp. 49—5° and 

 Fig. II. 



