552 Palaeontologie. 



familiär type of Myeloxyloti Landnot ii , the hypodermal Strands of 

 sclerench3'^ma preserving a straight course with little or no anastomosis. 

 The leaf-bases and petioles have also a Myeloxylon character, with 

 numerous bundles, but the structure of the bundles is concentric. 

 Each bündle is surrounded hy a ring ofsmall Strands ofsclerenchyma, 

 and secretory organs, probably of the nature of gum-canals, are 

 frequent. 



The Stern contains a Single large stele, of simple structure. In 

 transverse section, the stele measures 4.7 cm. in length by 1.8 cm. 

 in maximum breadth, taking the wood only into consideration. There 

 is no pith; the wood extends to the centre, and is in all parts 

 uniformly composed of tracheids interspersed with xylem parenchj^ma. 

 In this respect the stele of Stitdiffia resembles that öf Heterangimn , 

 or a Single stele of Mediillosa nnglicn. The wood is exarch, and the 

 stelar tissue almost wholly primary; secondary growth only having 

 taken place to a trifling extent. The most peculiar feature of the 

 Stern is the presence of large, irregulär masses of wood (surrounded 

 by phloem) around the stele, sometimes detached from it, sometimes 

 still in connection. The masses vary much in size. These meristeles 

 are fully described and illustrated, and their course traced. On 

 leaving the protostele, the meristele subdivides into Strands of very 

 unequal dimensions, and meristeles of distinct origin frequently 

 fuse together, lorming a network round the stele. The portion of the 

 meristele passing outwards eventually divides into typical foliar 

 bundles. 



Sntcliffia is unique in that the protostele persists as the main 

 vascular axis of the stem, while giving off a peripheral System of 

 subsidiary steles or meristeles, which form the points of departure 

 for the actual leaftraces. It is possible that we have in this genus 

 the first beginning of dialystelic structure. On this view Sutcliffia is 

 the most primitive of the Medullosece. 



The histology is next dealt with. The xylem in all parts is 

 exarch, and the walls of the larger tracheids bear multiseriate 

 bordered pits. The phloem of the stele and meristeles consists of 

 Strands of narrow Clements (sieve-tubes) embedded in parenchyma; 

 that of the leaf bases and petioles of numerous large Clements, 

 probably of the nature of sieve-tubes. Secretory canals traversed the 

 pericycle and cortex. 



After giving diagnoses of the genus and species, the Author 

 passes on to discuss the affinities of this plant. Although Sutcliffia 

 is referred to the famil}^ Medullosece on account of its general 

 Organization, it differs from the members of that family in the stem 

 having a Single main stele in a central position, and in the concentric 

 structure of the foliar bundles, both unique features among these 

 plants. Sutcliffia appears to represent the unique case of dialystely 

 originating without siphonostely. The foliar bundles retain more of 

 a stelar character than those of Medullosa , and represent a stage 

 on the Upgrade of development. It is doubtful if Sutcliffia lay on 

 the direct line of descent of any of the more complex types of the 

 Medullosece with which we are acquainted. It had not advanced 

 very far beyond the simple protostelic condition of Heterangium 

 among the Lyginodendrece , or of Megaloxylon. Thus there are 

 mdications that the whole course of evolution from the protostele to 

 the most elaborate dialystelic type may have been gone through 

 within the family Medullosece. Sutcliffia also adds probability to the 

 Suggestion that the Medullosece , as well as the Lyginodendrece , may 



