390 Watson >• — On Mesostrobus , a New Genus of 
which bears them in T me sip ter is, and the sporophyll of the Sphenophy Hales, 
particularly 5. majus . This involves the assumption that Tmesipteris is 
related to the Lycopodiales. 
The resemblance between the wood of Cheirostrobus and that of 
Lepidodendron is real, but does not extend to details. It seems to me that 
these resemblances are just what one would expect. 
The resemblance really depends on the fact that exarch protoxylem is 
primitive, at any rate, in the case of microphyllous plants. It has been 
shown by Dr. Scott that this is the case in the Cordaiteae, the Cycadofilices, 
and the Calamariales, a very varied set of plants. 
A medullated monostele is a very simple type of wood, and the fact 
that both Cheirostrobus and Lepidodendron have leaf-traces so small that 
they only take away a few tracheids from the edge of the wood, explains 
the fact that neither plant has the wood broken up into bundles. 
The second reason for regarding the Lycopodiales as allied to the 
Sphenophyllales is dependent on the assumption that the Psilotales are 
connected with the Lycopods ; so far as I know the evidence for the latter 
connexion is not much stronger than the first. 
Even if the Sphenophyllales are at all closely connected with the 
Lycopodiales (and that they are connected in some degree I do not wish to 
deny) it has yet to be shown that the primitive ancestor had a sporophyll of 
the type of S'. Dawsoni or S. trichoma to sum. As Dr. Scott pointed out in 
his original description of Cheirostrobus , that cone seems to be in many 
ways the most primitive of the known Sphenophyllaceous cones. I do not 
see how the Spencerites cone could be derived from a cone at all resembling 
that of Cheirostrobus . 
Finally, the idea advocated by Miss Sykes that the f ventral hump’ 
of Spencerites , the sporangiophore of Palaeostachya , and other similar 
structures are of axial origin and homologous seems to me to rest on 
a misconception of the nature of the evidence. 
The idea seems to one, who, like myself, was not trained in the ideas of 
rigid morphology, derived from the higher Angiosperms, rather forced when 
applied to Tmesipteris , but when extended to the cones of the Lycopodiales, 
none of which show the slightest trace of such derivation, it seems quite 
inconceivable. 
Summary. 
The new genus Mesostrobus is founded for a small Lepidodendroid cone 
(M. Scottii sp. nov.) from the Mountain 4 ft. Mine of the Lancashire 
Lower Coal Measures. 
The cone strongly resembles that of Lepidostrobus , but differs in the 
fact that the sporangium is only attached to the distal half of the horizontal 
