374 



Messrs. W. E. Duns tan and T. A. Henry. 



oblique annulus, and by the small output of bilateral spores. The 

 sporangia of the same sorus are not developed simultaneously. 



Anatomy. — The horizontal creeping rhizome, which is thickly covered 

 with stiff ramental scales, contains a tubular stele limited both in- 

 ternally and externally by a definite endodermis. The xylem is 

 mesarch in structure ; the protoxylem groups of spiral tracheids occur 

 in association with a few parenchymatous cells at regular intervals in 

 a median position. At the point of origin of each leaf the tubular 

 stele opens, and becomes U-shaped in section, the detached portion 

 passes into the petiole as a horseshoe-shaped meristele of endarch 

 structure. The meristele alters its form a short distance below the 

 origin of the lamina, and becomes constricted into two slightly unequal 

 portions ; from the lower end of one of these a small vascular strand 

 is gradually detached, and at a higher level a similar strand passes off 

 from the other half of the stele. During their passage into the main 

 ribs of the lamina the vascular strands, which are at first simply curved, 

 become annular, and assume the form characteristic of Marsilia. The 

 slender and branched roots are traversed by a triarch stele. 



Geological History. — The genus Dipteris represents a type which had 

 descended from the Mesozoie period with but little modification. The 

 genera Dictyophyllum and Protorhipis are regarded as members of the 

 Dipteridinse, which were widely distributed in Europe during the 

 Ehaetic and Jurassic periods. Records of these fossil forms have been 

 obtained from England, Germany, France, Belgium, Austria, Switzer- 

 land, Bornholm, Greenland, and Poland ; also from North America, 

 Persia, and the Far East. The genus Matonia, especially M. pedinata 

 (E. Br.), possesses certain features in common with Dipteris, and this 

 resemblance extends to the fossil types of the Matoninese and Dipteri- 

 dinse. Matonia pedinata and Dipteris conjugata, growing side by side 

 on the slopes of Mount Ophir in the Malay Peninsula, survive as 

 remnants from a bygone age when closely allied ferns played a 

 prominent part in the vegetation of northern regions. 



" The Nature and Origin of the Poison of Lotus arabicus." By 

 Wyndham E. Dunstan, M.A., F.E.S., Director of the Scien- 

 tific and Technical Department of the Imperial Institute, and 

 T. A. Henry, B.Sc, Salteus' Company's Eesearch Fellow in 

 the Laboratories of the Imperial Institute. Eeceived May 30, 

 — Eead June 20, 1901. 



(Abstract.) 



The authors have already given a preliminary account* of this 

 investigation and have shown that the poisonous property of this 

 * 'Roy. Soc. Proc.,' vol. 67, p. 224, 1900. 



