1046 
de Fr aine. — On the Structure and 
an exactly similar peculiarity has been described by Scott 1 as occurring 
occasionally in the secondary xylem of Medullosa anglica. 
2. Structure of the Phloem . The primary phloem is not preserved 
around the steles and ‘ meristeles ’, but a broad zone of secondary bast, 
usually very badly crushed, extends entirely or almost entirely round them ; 
here and there the preservation is sufficiently good to enable some details 
of its structure to be observed. In most cases the zone appears to have 
attained considerable thickness, though lateral crushing has undoubtedly 
exaggerated the appearance to some extent. 
The phloem elements are arranged with great regularity, the radial rows 
corresponding with the tracheidal series of the wood, while the medullary 
Text-fig. 13. Transverse section of second ary phloem, x 105. fib. — thick-walled elements 
of phloem ; m.r. = medullary ray ; s.c, = secretory element. 
rays are an extension of those present in the xylem. The phloem elements 
resemble those described by Solms-Laubach 2 as occurring in the secondary 
phloem of Medullosa Leuckarti , and by Scott 3 in M. anglica ; they appear 
to have thick cell-walls, so that the lumen in transverse section appears as 
a dot (Text-fig. 13). For reasons detailed in his paper, Solms-Laubach 
regards these elements as sieve-tubes, and this conclusion Scott considers as 
probably correct. The latter observer offers two suggestions to account for 
the thick-walled appearance presented by the elements. 
The cell-walls may have been thin walled during life, swelling up greatly 
under the influence of maceration and decay in the period before petrifaction ; 
1 Scott: Medullosa anglica, loc. cit., p. 90. 
2 Solms-Laubach : Uber Medullosa Leuckarti. Bot. Zeit. , 1897, p. 179. 
3 Scott: Medullosa anglica , loc. cit, p. 90. 
