Anatomy of the Cone and Fertile Stem of Equisetum . 253 
branches, usually a number equal to the number of traces and bundles, 
is given off in the region of the node. The incoming stele of the branch 
forms a continuous ring or cylinder, joining on obliquely to the adjacent 
ends of two neighbouring bundles (Pfitzer, pp. 329-30). I have sometimes 
observed similar but arrested branches in sections of fertile stems of 
E. maximum. In some cases these branches of the fertile stem are fully 
developed, as recorded by Milde in the variety frondescens { A. Br. 1844) of 
E. maximum (Milde, p. 249). Though the branches I observed never 
reached the periphery of the stem, their vascular system bore the same 
relation to that of the main stem as did the vascular system of the fully 
developed branches to the main stele of the vegetative stems, and there 
seems no reason to doubt that this is true of the branches of the fertile stem 
of the variety frondescens. The fertile stem bearing Cone D also bore two 
abortive branches, but the relations of their vascular tissue to that of the 
stem were very different. Both were inserted on the internode, or what 
would normally be an internodal part, between the annulus and the upper 
vegetative whorl. These two branches never become really free from the 
stem, but form a projection or hump over part of the circumference of the 
latter. Both these projections or abortive branches contain a vascular 
system which is connected with that of the main stem towards the upper 
end of the projection. In other words, the free end and organic apex of the 
vascular system of the hump projects downwards ; but, as the parenchyma¬ 
tous tissue in which it is embedded is congenitally united with the stem, it 
follows that the lower cells of the hump or abortive branch must have been 
produced first. The stem being quite mature when cut, it is impossible to 
say whether the lignification of the branch stele proceeded in a downward 
direction, viz. from the point of insertion of the branch stele on the main 
stele ; or upwards until eventually a junction was effected between the 
steles of branch and stem; or whether lignification began in the middle 
region of the hump and proceeded both upwards and downwards. One effect 
of the downward direction of the branch steles is that the stele of the main 
stem is larger and contains more bundles above than below their insertion. 
The larger and abortive branch contains in its middle region, that 
in which the stele is most developed, eleven bundles. Of these the five 
outermost bundles, forming an abaxial arc, open adaxially, constitute the 
continuation, in a steeply downward direction, of five adjacent bundles 
of the main stem. These bundles pass out in their entirety, but as they 
are constricted off as a loop of distinct bundles they leave no gap in the 
main stele. The remaining six adaxial bundles of the branch stele are 
derived from four other bundles of the main stem. These four bundles do 
not themselves pass out, but each bundle divides in a plane approximately 
coinciding with a line laterally across the bundle as seen in transverse 
section. The outer series of bundles then passes out, diverging slightly 
