Anatoiny of the Cone and Fertile Stem of Equisetum . 261 
Though other figures of Palaeostachya , notably one of P. gracilis , Ren., 
reproduced by Solms-Laubach from Zittel’s text-book (Solms, p. 332) and 
again by Jongmans (Jongmans, p. 322), show shorter and more nearly 
horizontal sporangiophores, it would seem that even in old age the sporangio- 
phores could hardly have been much reflexed as they would soon have 
come to rest on the surface of the subtending bract. From the latter they 
are only separated by the thickness of the sclerized band and by the 
additional space left by the slight downward ‘ bowing * of the bract at 
its base. 
To judge from Hickling’s figure the actual distance in a downward 
direction traversed by the sporangiophore trace of Palaeostachya vera seems 
to have been rather less than 1*3 mm., while in extreme cases in E. maximum 
it is as much as 1*5 mm. of the part. Cone B, however, in which this height 
was recorded, seems to have had a stelar diameter of more than twice that 
of the Palaeostachya described by Hickling ; the sporangiophores of the 
latter genus seem, too, to have been smaller and provided with fewer 
sporangia than those of E. maximum. 
Hickling mentions the fact that though Palaeostachya shows no 
regular alternation of the bundles in successive internodes of the stem, 
occasional irregular communications seem to have occurred between adjacent 
bundles. As pointed out in the previous pages an irregular alternation of 
the bundles of successive nodes occurs in the cone of Equisetum , where it is 
due to a reduction of xylem at the nodes. It would be interesting to know 
if the same explanation applied in the case of P. vera. 
The cones of E. maximum also recall those of Calamostachys 
Binneyana in one point. In both cones some of the traces have undergone 
torsion while passing through the cortex (Hickling, 2, p. 10). In Calamo¬ 
stachys, however, it is not the traces of the sporangiophores but those 
of the bracts that pursue a curved course, and the curvature is throughout 
a whorl in the same direction. Hickling regards this curvature as ‘ the 
only possible explanation of a well-known difficulty in the morphology 
of this cone—viz. the combination of superposed sporangiophores and non¬ 
alternating bundles with alternating bracts’ (Hickling, 2 , p. 10). In 
E. maximum the torsion, which may be to right or to left, results from the 
fact that the persistence of relatively wide tracts of parenchyma at the node 
causes the incoming traces to curve in order to attach themselves to 
a bundle. 
Summary. 
1. The xylem of the axis of the cone of this species is more reduced, 
relatively to its size, than that of the axes of the cones of E. arvense and 
E. palustre , but slightly less so than that of the corresponding region 
in E. limosum. 
