410 SPHENOPHYLLALES. B. PSILOTACEAE 
unbranched, though occasionally a dichotomy may be observed (Fig. 226 a), 
The aerial shoots differ from the rhizomes in bearing appendages: first, 
small scale-like bodies are produced, but higher up they enlarge gradually, 
till the condition of the fully-formed foliage leaf is attained: this is about 
half an inch long, and flattened in a vertical plane. The basal vegetative 
region is continued directly into the fertile region: here the distinctive 
feature is the forked sporophyll,! which bears the sporangiophore seated 
at the fork, and on its adaxial surface: each sporangiophore supports 
two large and confluent sporangia (Fig. 226 B, c). The disposition of 
the leaves upon the mature axis is irregularly alternate, and this appears 
in transverse section of the apical bud (Fig. 227): here the axis shows 
ace 
OSS IS" 
cK) © 
Fic. 227. Fic. 228. 
Transverse section through a spor- Tmesipterts tannensis, various unusual forms 
ferous bud of Smesipteris, ax= of sporophyll and sporangiophore ; in i. the syn- 
a J/=foliage leaves. @=lateral angium 1s abortive ; in ii. and iii. one loculus is 
lobes. sy=synangia. X20. abortive ; others show a larger number of loculi 
than two; others again, right and left on the 
lower row, show a single loculus, the septum 
being imperfect, or absent. 
a very irregular outline owing to the decurrent bases of the appendages: 
it is also apparent that these are alternate: it may also be noted that 
in the case figured three foliage leaves (/) are inserted above the three 
sporophylls (4 sy, @). 
The fertile region forms a very lax strobilus, in which the following 
features may be noticed. It does not differ markedly from the vegetative 
region in the size of the parts which it bears: it is not composed exclusively 
of sporophylls, but foliage leaves of the usual type may be interspersed 
‘The terminology here used is that of Scott (Studies, p. 479). I regret having in 
1893 (Séedees, part i.) used the term sporangiophore in a wider sense than here, so 
as to include the bifid sporophyll itself. Such an extension of the term obscures the 
natural comparisons not only with the Sphenophylleae, but also with other sporangio- 
phoric types. It is best to restrict the use of the word in the Psilotaceae to the 
body borne by the bifid sporophyll, often designated also the synangium. The various 
opinions previously held as to the morphology of these appendages need not be discussed 
again here. It will suthce to refer to my Stadzes, i., p. 539, where they have been 
considered at some length, with references to the literature relating to them. See 
also Lignier, Bul. Soc. Linn. de Normandie, 1904, p. 95,.and footnote. 
