Sykes. — The Anatomy and Morphology of Tmesipteris. 81 
a forked bract. It will be necessary to consider some of these views in 
greater detail. 
Foliar Theory. Dangeard 1 suggests that two leaves have coalesced 
by their petioles, and have given rise to a synangium at the point where 
this union ceases. The mere fact that the sporophyll trace has a single 
and not a double origin appears to me sufficient to dispose of this theory. 
If we are to consider that two leaves have fused and given rise to a sporo- 
phyll, we should certainly expect that their traces, even if not distinctly 
separate, would at least originate from two separate protoxylem groups 
of the stem-stele. 
The other members of the foliar school suppose the sporophyll to be 
a single-lobed leaf. Bower 2 ‘ understands the synangium to be a lateral 
organ, originally foliar in nature, and an outgrowth from a single lobed 
leaf’. He thus homologizes the synangial apparatus in Tmesipteris with 
a single Lycopodian sporophyll. 
Thomas 3 lays great stress on the presence of green assimilating cells 
and stomata in the stalk of the sporophyll. But when we take into 
consideration the fact that the two leaves of the branch have, like all the 
other leaves of Tmesipteris , decurrent bases, it is not surprising to find 
leaf tissue on the sides of the branch. Also in the nearly allied plant, 
Psilotum , we find assimilating tissues in the stem itself. To support his 
view Thomas brings forward certain abnormal cases in Tmesipteris— 
sporophylls with repeated dichotomy and two or three synangia ; sporo- 
phylls with a long stalk instead of a short pedicel ; and cases in which the 
synangium was replaced by a leaf lobe of normal appearance, the whole 
branch then being comparable with a tri-lobed leaf. The examples of 
repeated dichotomy generally occurred at the region of maximum develop- 
ment of the plant, and are supposed by Thomas to be dependent on abun- 
dant nutrition ; but Text-f g. VII, p. 72, also represents a second dichotomy 
seen near the apex of the plant. It seems to me easier to regard this kind 
of abnormality as the repeated dichotomy of a branch than as the lobing 
of a leaf. The occasional presence of a long stalk to the synangium also 
suggests that the usually short pedicel is of an axial nature. The third 
abnormality is of less value, being obviously a monstrosity. 4 
Scott considers the foliar view of the sporophyll in Tmesipteris as of 
great interest in that it throws some light on the relation of that plant to 
Sphenophyllum and Cheirostrohush 
Axial Theory. The axial theory of the sporophyll in Tmesipteris is 
too simple to need much exposition, and some of the arguments have 
been given above. It appears to me that the chief of these is to be found 
1 Dangeard, Le Bot., ii. 2 Bower, 1894. 
5 Thomas, 1902. 4 Scott, 1907, p. 139. 
* Scott, 1897, Proc. Roy. Soc., p. 1 1 7, and 1897, Phil. Trans., p. 27, and Studies, 1900. 
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