PRESENT POSITION OF PALEOZOIC BOTANY—SCOTT. SS) 
wood from the angles of which the leaf traces arise. A secondary 
or exogenous wood was also developed; in the coal-measure species 
the tracheides are provided with multiseriate pits. The leaves, borne 
in verticils at the nodes, are typically cuneate, with dichotomous 
nerves, but may be divided into numerous linear segments; they are 
usually six in number and not alternating in the verticils as in the 
KEquisetales. The sporangia are varied in grouping, and are borne 
on the lobes of more or less modified fertile leaves. (Fig. 1.) The 
nervate sporangiophores are sometimes peltate, and the sporangia 
(one to four in number) are usually borne on the ventral lobes, 
though in one species they are also present on the dorsal. The cur- 
rent statement that they are heterosporous ap- 
pears to be erroneous. 
The:-Cheirostrobus cone, from the Lower Car- 
boniferous, is of great complexity, and is in fact 
the most elaborate Pteridophytic fructification 
known to us. <A stout axis with a polyarch 
stele of primary wood containing no pith, 
bears numerous verticils of highly compound 
sporophylls. (Fig. 2.) Each sporophyll con- 
sists of six segments, of which three are dorsal, 
sterile, bract-like organs, the remaining three 
constituting ventral peltate sporangiophores, 
each of which bears four sporangia. 
Intimately related to the Sphenophyllales, if 
not referable to the same class, is Pseudobornia, 
described by Nathorst from the Arctic Upper |. Neh eae ae 
Devonian and made the foundation of the order — majus. Part of forked 
Pseudoborniales. The main stems, which are  ®Porephyll in surface 
. % . ‘ view, showing a group 
believed to have been creeping, are of consider- — of four sporangia in- 
able size, reaching about LO mm. in diameter in erted Below & bitin 
their present flattened condition. The stem was 
articulated and branched, and on the smaller branches the whorled 
leaves are found in position. Several are borne in a verticil, the 
number being most probably four; each leaf is of a highly com- 
pound form; seated on a short petiole, it divides by repeated dich- 
otomy into several leaflets, which are themselves deeply pinnati- 
fied, with numerous fine segments. The fructification is in the form 
of long, lax spikes, bearing whorled sporophylls, resembling reduced 
vegetative leaves. A sporangium appears to have been borne on 
the lower part of the sporophyll, but there is no information as to 
its mode of insertion. Indications of probable megaspores were ob- 
served. Unfortunately the type is at present known only in the 
form of impressions. 
41780—08——28 
