PRESENT POSITION OF PALEOZOIC BOTANY—SCOTT. a wi 
esting analogy with the foliage of Psewdobornia and the Sphenophy!l- 
lales. The leafy branches have been divided among the genera Annu- 
laria, Asterophyllites and Calamocladus. 
The anatomical structure of all parts of the plant is now known 
in a number of instances, but the correlation of the various organs in 
their different states of preservation still presents great difficulties. 
The anatomy of the stem in its young condition is closely similar to 
that of a recent Lquisetum and thus deviates widely from the Spheno- 
phyllaceous type. The usually fistular pith is surrounded by a ring 
of collateral bundles, each, as a rule, accompanied by its carinal 
canal, in which the disorganized remains of the spiral tracheides can 
be detected. Thus the development of 
the wood was in these cases wholly cen- 
trifugal. A certain amount of centripe- 
tal xylem is, however, present in one 
species, Calamites pettycurensis, from 
the Lower Carboniferous of Scotland, 
lying on the medullary side of the cari- 
nal canals. In all except the youngest 
twigs a zone of secondary wood and 
bast, often of great thickness, has been 
formed by means of a normal cambium, 
the cells of which, together with those 
of the phloem, can be.observed in favor- 
able cases. In Calamites itself (the 
Arthropitys of Goeppert) the secondary 5, 3- catamostachys. Diagram 
wood is of a simple structure compar- of _cone in radial section. az, 
able to that of the less differentiated  2Si» WPtrh Dre (br) ait pelea te 
Coniferous woods, but usually with — sporangiophores (sp); sm, spo- 
: say: rangia borne on the sporangio- 
more or less scalariform pitting on the  jnores. As the bracts are alter- 
tracheides. Calamodendron, from the nate with one another their up- 
Upper, and Arthrodendron from the ee ica ere ten a 7p 
Lower Coal-Measures are characterized 
by the complex structure of the principal medullary rays, which 
contain much fibrous tissue in addition to the usual ray-parenchyma. 
In their vascular anatomy, the Equisetales show a marked advance 
on the Sphenophyllales; in this respect they reach the level of the 
simpler Gymnosperms or Dicotyledons—an interesting example of 
parallel development. 
The fructifications of the Calamariacee are of several different 
types, nearly all of which show an evident relation to the well-known 
strobilus of Z'guisetum though usually of more complex organization. 
They represent several genera described as Calamostachys (the most 
common; see fig. 3), Palwostachya, Cingularia, Pothocites, and Equis- 
etites, The cones of these types show considerable variation in the 
