The Present Position of Palaeozoic Botany. 16 1_ 



Yet another form of fructification, the genus Cingularia, of Weiss, 

 has been referred to Calamariaceae or placed provisionally between 

 that class and the Sphenophjilales. The chief character is that the 

 sporang'iophores. which are not peltate, and are described as bearing 

 4 sporangia on the lower surface, are inserted immediatelj' heJoiv the 

 verticil of bracts, with which, according to the latest observations, 

 they seem to have been partially fused. This curious arrangement 

 suggests the dorsiventral lobing of the Sphenophyllaceous sporophyll 

 in an inverted form, but the example of Palaeostachija w^arns us that 

 in the absence of structural evidence such interpretations are highly 

 precarious. It may be that, as Lignier (1903) has suggested, Cingu- 

 laria represents an exaggeration of the displacement which we find 

 in CaJamosfachys, the sporangiophores, in spite of appearances, really 

 belonging to the sterile whorl below. 



Relation of Equisetales and Sphenophyllales. 



The general morphological agreement between the two classes is 

 manifest, as shown by the articulated stems with constant verticillate 

 arrangement of the appendages. Archaeocalamites, the oldest of the 

 known Equisetales, distinctly approaches the Sphenophyllales in the 

 superposition of the verticils and in the dichotomously divided leaves. 

 In many Calamariaceae the individual leaves resemble the leaves or 

 leaf-segments of the plurifoliate SphenopliyJlums so closelj" that the 

 external characters scarcely allow of a distinction between the two 

 groups. 



These, however, are only outward resemblances. Lignier has 

 endeavoured to place the comparison on an anatomical basis. In the 

 typical species of SplienophyUmn there are 6 leaves in a whorl, but 

 the vascular bundles supplying each two leaves start from the same 

 angle of the triarch stele. Hence Lignier infers that three was the 

 original number of leaves in a verticil. In some species the increased 

 number of leaves has affected the stele itself, each of its three 

 angles being double. In cases wiiere the leaves are further segmented, 

 a further forking of the bundles within the cortex takes place. In 

 the Calamariaceae the increased dimensions of the stem have involved 

 a corresponding multiplication of the leaves and of the bundles in 

 the axis. But in cases like the fructification of Calamostadnjs we still 

 have a clear analogy with Sphenopliyllum in the fact that each two 

 bracts receive their vascular supply from the same axial bundle, while 

 in other instances (e. g., PaJaeostachya vera) the axial bundles are 

 themselves duplicated, forming evident pairs. There are thus ana- 

 tomical grounds for believing that the numerous leaves of a Calamité, 

 like those in certain forms of Sphenopliylhm, represent the segments 



Progressus rei botanicae I. 1^ 



