1050 
de Fr aine. — On the Structure and 
cells did exist, and is being disorganized ; no sign of the early stages of 
development, such as are figured by Seward, were to be traced. In all the 
secretory elements so abundantly scattered throughout the specimen evidence 
of the secretion is seen either in the form of black carbonaceous matter, 
light coloured contents, or the appearance of vacuolation, but in no case 
have any of these signs of contents been observed in the large elements of 
the phloem. Longitudinal sections were not available for examination, but 
from Scott’s observations on S. insignis , they are known to be long tubes. 
On the whole the new specimen does not materially add to the evidence 
which would elucidate the question of the nature of the elements in question. 
The absence of any sign of secretion and the distribution of the elements in the 
Text-fig. 16. Transverse section of a leaf-trace bundle showing periderm formation, x 70. 
pd. = periderm ; xy x . = primary wood. (Xylem slightly restored.) 
phloem (where the presence of such numerous secretory elements appears 
to be unparalleled) would incline to the view that they represent sieve-tubes. 
An interesting feature occurs in two of the leaf-traces at the upper end 
of the stem. The bundles are of the unilateral type, and no phloem is 
present ; but immediately surrounding the primary wood a zone of peri- 
derm occurs (Text-fig. 16). The tracheides of the primary wood have 
obviously been injured in some way, probably by fungal growth, and 
the leaf-traces in consequence are being isolated by means of a periderm 
formation. A precisely similar case of isolation of a vascular strand which 
had been injured by a fungal attack has been observed in the hypocotyl of 
a seedling of Allionia albida. 
