162 MBDULLOSEAB [OH. 



as Medullosa in the Medulloseae, is probably correct. There is 

 clear evidence of a close bond of union between recent Cycads 

 and the Medulloseae, and Sutcliffla offers a possible means of 

 deriving complex polysteUc types from a monostelic ancestor. 



Worsdell's opinion^ that the stele of Lyginopteris affords 

 «vidence of derivation from a polysteHc ancestor and is not homo- 

 logous with the true monostele of Heterangiuni is opposed to the 

 undoubted signs of intimate connexion exhibited by these genera. 

 The Lyginopterideae are, as Scott^ says, a less advanced group 

 than the Medulloseae and, it may be added, they are more remote 

 from the modern representatives of the Cycadales. The Lygino- 

 pterideae and the Medulloseae are probably offshoots of a common 

 stock, but the Medulloseae occupy a position farther removed 

 from the fihcinean ancestry than Heterangium and Lyginopteris^ - 



The relative meagreness of our knowledge of the reproductive 

 ■organs of the Medulloseae gives precedence to anatomical data 

 in phylogenetic considerations, but the evidence furnished by 

 Trigonocarpus and other seeds that may fairly be assigned to 

 Medullosan plants is in harmony with the conclusions based on 

 vegetative characters with regard to a close affinity between the 

 Medulloseae and Cycads. 



The comparative examination of recent Cycads naturally 

 suggested by any attempt to compare the group as a whole with 

 Palaeozoic types leads to some apparently contradictory results. 

 The habit of the megasporophyU of Cycas is usually quoted as 

 a primitive attribute : the close resemblance in plan and in manner 

 of occurrence on the stem between megasporophylls and foUage 

 leaves recalls both Perns and Medullosan fronds. On the other 

 hand the production of eight body-cells in the pollen-tube of 

 Microcycas^ in place of the usual single cell may also be regarded 

 as a primitive character. It is perhaps possible, as Miss Dorety^ 

 says, that the polyspermy may be a case of recurrence and not 

 a direct inheritance. Microcycas differs from Cycas in having 

 only one vascular cylinder, and if the presence of several concentric 



1 WorsdeU (06) pp. 140 et seq. 2 Scott (09) B. p. 464. 



" For a general summary of ' Pteridosperm anatomy and its relation to that of 

 the Cycads' see Bancroft (14). 



* See p. 6. '^ Dorety (09^} p. 144. 



