442 BOTANICAL GAZETTE [NOVEMBER 
bundle of xylem, resulting in a fernlike state, comprising two 
bundles of xylem facing each other, with phloem outside (fig. 7). 
The relation of pines to the fern stock is further emphasized by 
the occurrence (in the wood or periderm of tumor needles) of all 
transitional forms, from 
normal pitted elements 
to scalariform cells, such 
as are present in ferns, 
and restricted to endo- 
dermal cells of normal 
needles.® 
3. RELATION OF 
PINES TO GNETALES.— 
Scalariform cells in pine 
.—Tumor of Coccus resinifians on pine 
Fic. 5 
needle (collected at Arcachon, dunes of Abatilles, 
June 1917): part of periderm (schematic); e, endo- 
are much more abundant in tumor than in sound 
neighboring tissue); d‘, lignified cells of hyperplasia 
due to infection by Coccus; b, epidermis and hypo- 
derm; x, normal wood; hloem; x', inverse wood 
(staining red with eosin and green with methy] 
green) and of vessels staining orange with Sudan 
III; this inverse wood develops from ventral face 
of protoxylem to endodermis, and is homologous 
with inverse wood in cycads. 
needles may be compared to the tracheae 
in Gnetales, and suggest the origin of 
both from a common fern stock. Fic. 6.—Part of fig. 5: ', 
4. RELATION OF PINES TO EqutsE- Phloem; w, lignified vessels 
23 ° normal w same in inverse 
TALES.—The origin and evolution of the wood; j, lignified cells with 
protoxylem is strikingly similar in pine hyperplasia. 
ood; 2, 
’ The perforations in the scalariform cells of pines may be explained as derived 
from the fusion of enlarged bordered pits, as claimed by Tomson for Gnetales; but 
the reverse is probably true, bordered pits being derived from ancestral simple incom- 
plete perforations by acquiring highly specialized characters. 
