500 : BOTANICAL GAZETTE [DECEMBER 
All stages between the juvenile type with the solid stele and the adult type 
may occur; cases of reduction of steles of the adult type to the juvenile con- 
dition are described. ‘These variations are held to be dependent upon physio- 
logical factors; the solid stele of the juvenile type is considered to be merely a 
physiological variation of the general type of the species. 
The outer xylem of the leaf trace, after separation from the stele, curves 
round the protoxylem strand; at the same time, the trace, originally monarch, 
becomes diarch by the division of the protoxylem strand. These two processes 
result in the formation of a trace whose cross-section shows two protoxylem 
points, ‘each surrounded by metaxylem. This “clepsydroid” stage of the leaf 
trace is characteristic - certain of the Zygopterideae and affords data for a 
comparison with that 
he branches ie feo the vestigial axillary buds. There is no 
vascular connection between the branch stele and the leaf trace immediately 
below, as in some species of Botrychium. Immediately below the point of 
origin of a branch, accessory xylem is developed by irregular divisions of the 
parenchyma within the phloem. While no cambium is present, this is con- 
sidered to be a form of secondary thickening. In the base of the branch this 
accessory xylem surrounds an extension of the inner metaxylem of the main 
axis, thus forming a solid xylem strand which is in all respects similar to the 
steles of rhizomes of young plants. The further ra ine of the branch 
stele is identical with that of steles of young plan 
e mesarch character of the stele, the tae stage of the leaf trace, 
the irregular secondary thickening of the stele, and the connection of the 
branch stele with the main axis rather than with the leaf trace, all emphasize 
the view of relationship of the Ophioglossaceae to the Zygopterideae. It is 
further pointed out that these features also afford a basis for comparison with 
certain of the Cycadofilicales—L. C. Petry. 
Origin of dwarf plants.—Stout™ has described a dwarf form of Hibiscus 
oculiroseus which differs from the usual robust type in having more basal 
branches, shorter internodes, and smaller, somewhat crinkled and irregular 
leaves. The dwarfs are descendants of a single robust plant with some 
crinkled leaves and somewhat shortened upper internodes, a type known as 
“intermediate.” Four other plants have given none but normal robust off- 
spring, something over 100 in all. Selfed seed from the intermediate plant 
yielded one dwarf, 3 intermediates, and 11 robust plants. From selfed seed 
of one robust plant, there were grown one intermediate and 33 robust plants. 
Selfed seed of the one dwarf plant produced one robust, 8 intermediate, and 72 
dwarf plants, the robust plant being apparently an accidental hybrid. These 
results are compared with the behavior of dwarfs of Oenothera, peas, and sweet 
12 Stout, A. B., The origin of dwarf nat as shown in a sport of Hibiscus oculiro- 
seus. Bull. Torr. Bot. Club 42:429-450. 191 
