4i 
The So-called Phloem of Lepidodendron. 
carried out in recent plants by elements possessing the structure of 
phloem, were in Lepidodendroid stems performed by tissues of a 
somewhat different type ; probably the secretory zone of the stem 
and the secretory elements of the leaf-traces are physiologically 
comparable to phloem tissue, and in part to the laticiferous tissues 
in some recent plants.” 
Professor Weiss has recently published an account of certain 
tissues in some exceptionally good specimens of Lepidodendron 
fuliginosum from the Cash collection of plants in the Manchester 
Museum 1 . His main object is to show that the tissue which I 
called the secretory zone does not differ materially from the phloem 
of recent Lycopodiaceas—“ Until it is disproved,” he writes “ that 
the cells of this phloem region are of such a nature as not to be able 
to effectively conduct and store organic material for the use of the 
secondary meristem we must look upon it as functionally representing 
the phloem, though it may differ from it in construction. But as a 
matter of fact it does not seem to differ materially from the phloem 
of recent Lyeopodiacece except in such particulars as are probably 
connected with the absence of secondary thickening in recent Lycopods 
and the consequent diminished need of storing organic materiaj 
within the stele.” . . “ That some of the elements of the phloem 
region may have been of the nature of laticiferous cells or may have 
united to form mucilage ducts is, of course, quite conceivable, even 
when the bulk of the elements made up a true phloem.” 
I am in agreement with Professor Weiss as regards the probably 
phloem-function of this tissue 2 , but I do not agree with his conclu¬ 
sions as to its phloem-structure. The same writer goes on to say that 
he agrees with Dr. Scott 3 in regarding the phloem of Lepidodendron 
as fundamentally similar to that of the recent allies of the genus. 
One of the photographs 4 reproduced in Professor Weiss’ paper 
shows the cambium distinctly; in the stem he describes, a fairly 
thick band of secondary xylem has been produced, but the connection 
between the cambial tissue and the outermost additions to the xylem 
is not brought out very clearly. It is important to notice that the 
region of active meristematic growth is separated from the most 
external thick-walled xylem elements (in Lepidodendron fuliginosum 
1 Weiss, 1901. 
2 Seward, 1899 P. 155. 
3 Scott, 1900. Studies in Fossil Botany , pp. 142, 143. 
4 Weiss, 1901. Fig. 2, PI. II. 
