3i6 



DIPTERIDACEAE 



[CH. 



up to a point close below the lamina (see Vol. I, Fig. i6i, r). These are all 

 relatively primitive characters, and they direct comparison downwards to 

 Matonia and Gleichenia. But D. Lobbiana, notwithstanding its smaller size, 

 shows a somewhat more advanced state, for here the leaf-trace springs from 

 the solenostele of the axis not as one but as two separate straps, given off 

 right and left from the margins of the foliar gap (Fig. 574, b). Each of these 

 divides almost at once into two {d, e), and the four strands arranged in 

 a curve pass outwards into the leaf-base, continuing as separate strands 

 upwards to the further branchings at the base of the lamina. This structure 

 appears as an advance upon that seen in D. conjugata, a fact that will be 

 considered later. Notwithstanding this disintegration of the trace the 

 underlying structure is the same as in D. conj?igata, and in this the genus 

 conforms to the type seen in Matonia and Metaxya, and ultimately in 



Fig. 574. a-/, successive transverse sections from below upwards, 

 showing the separation of the leaf-trace from the solenostele in 

 Dipteris Lobbiaiia. It is disintegrated from the first. ( x 3.) 



GleicJicnia. The latter is the most primitive example of it, being.protostelic: 

 but G. pectinata and Platyzoma show elaborations resulting in solenostely. 

 In Metaxya and Dipteris a simple solenostele, and in Matonia a polycyclic 

 state is seen, but still with undivided leaf-trace. The same appears in D. 

 Lobbiana, excepting that here the leaf-trace is disintegrated. Still the 

 anatomical facts for these Ferns, like those from the dermal appendages 

 which are never flattened scales except in Eu-Gleichenia, indicate a common 

 and a relatively primitive character for them all. 



SoRi AND Sporangia 

 The sorus of Dipteris is composed of a number of sporangia with which 

 numerous glandular hairs are associated. The sporangia show no regularity 

 of position or of orientation, such as is seen in Matonia or Gleichenia. There 



