of Lepidostr obits Brownii , Schpr. 337 
but even there, apart from the peculiar development of the 
endodermis, the correspondence is not so close in details of 
the cylindrical stele as that in the Psilotaceae proves to be. 
The absence of any definite layer of cells of the endodermis 
in Lycopodium is a distinctive feature ; and though in some 
species (e. g. L. Selago ) the xylem may be united into 
a connected stellate body, as seen in transverse section, still 
the correspondence is not in any 6 way a close one. On 
comparing with the Psilotaceae, however, the following points 
of resemblance may be noted — (1) the central thin-walled 
parenchyma resembles that well known to occur in Tmesi- 
pteris , though its place is taken in Psilotum by thick-walled 
sclerenchyma ; moreover it is to be remembered that this 
thin-walled central tissue is not a constant character in 
Lepidodendron : (2) the crenulated margin of the xylem 
corresponding to the star-like xylem of the Psilotaceae : 
(3) the definite layer of endodermis, corresponding to that 
already noted by De Bary 1 in Psilotum : this is shown 
in Fig. 3 B, which should be carefully compared with Fig. 3 A 
drawn from Brown’s cone, when the detailed resemblance 
of the two cannot be missed. M. Bertrand 2 describes the 
endodermis in Psilotum as not definitely characterized, and 
difficult to distinguish, and this is borne out by his Figs. 
173-17 6, though in his Figs. 161, 162, he draws the endo- 
dermis with the characteristic marking. I find, however, 
that though the cells of the endodermis do not form a per- 
fectly regular layer, there is no difficulty in tracing the 
sheath, after suitable treatment, by the usual characteristic 
structure of the radial walls. (4) The very slight bulk of 
the tissue referable to the phloem, and the absence of dis- 
tinctive characters in it. De Bary noted the narrowness 
of the band in Psilotum, , and a similarity of some of the 
elements to the sieve-tubes of Ferns ; this I can confirm. 
The closeness of correspondence of the tissues in the section 
of Lepidostr obus (Fig. 3 A) to that of Psilotum (Fig. 3 B) 
1 Comp. Anat., Engl, ed., p. 348. 
2 Arch. Bot. d. Nord. de la France, 1, p. 401. 
