132 Seward and Gowan .— The Maidenhair 
comparable on a small scale (Fig. 42) to the main stem of 
a Cycad. A short shoot may, after several years’ growth, 
elongate into a long shoot 1 bearing scattered leaves, and in 
some instances the short shoot may branch (Fig. 42), like the 
trunks of Cycas and some other genera of Cycads. 
In the long shoot the xylem and phloem form a complete 
ring ; secretory canals traverse the tissues of both pith and 
cortex, and secretory cells are especially abundant at the peri¬ 
phery of the phloem. The medullary rays of young long 
shoots were found to be usually one cell deep, rarely two or 
three cells in depth. The tracheids bear one to three rows of 
bordered pits on their radial walls, and when more than one 
row is present the pits of adjacent series may occur on the 
same level; single rows of pits are fairly abundant on the 
tangential walls of the xylem-elements. 
In comparing a series of sections cut through the upper 
part of a short shoot and the lower portion of the long shoot into 
which it has elongated, one notices certain differences in the 
structure. The wood of the short shoot is rather looser in 
texture (Fig. 58), more particularly at the inner margin of the 
xylem, where the rows of tracheids are separated by broad 
medullary rays as in Cycadean wood (Figs. 53 and 58). In 
the cortex of a short shoot the phloem is succeeded by 
ordinary parenchyma, including crystal-sacs; in the long shoots 
a broken ring of thick-walled and crushed secretory cells suc¬ 
ceeds the phloem, and farther out crystal-sacs are abundant 
in the parenchymatous tissue. Canals are met with in the 
pith and cortex of both long and short shoots. The pith- 
cells of the short shoots are more or less spherical and irregu¬ 
larly disposed, while in the long shoots they are more 
rectangular and in regular vertical series. With the exception 
of certain species of Ceplialotaxns , as recently pointed out by 
Rothert 2 , secretory canals are not found in the pith of true 
Conifers. In the short shoots the phloem is characterized by 
the occurrence of thick-walled fibres. Reticulately pitted 
tracheids are abundant at the point of exit of a leaf-trace, and 
1 Bertrand (’74), p. 24 . 2 Rothert (’99). 
