274 MORPHOLOGY OF ANGIOSPERMS 



uted. This fact seems to substantiate the claim as to the primi- 

 tive character of this family, and to discount the theory of its 

 origin as a reduction type. Not only did the screw-pine exist, 

 but the family was richer in forms than at present, all the 

 living genera containing more numerous species than now, and 

 at least one extinct genus having been recognized. 



A little later in the Cretaceous the Palmaceae occurred 

 abundantly, but in genera that are now for the most part 

 extinct. Their distribution was very wide-spread, remains hav- 

 ing been found in deposits from Greenland to Egypt. This 

 early association of Pandanaceae and Palmaceae is corrobora- 

 tive of the idea of their genetic relationship, and the later ap- 

 pearance of the Palmaceae further confirms the morphological 

 evidence that they may have been derived from the Panda- 

 naceae. 



The Potamogetonaceae were abundant, a fact that coincides 

 well with their morphological position as the most primitive 

 of the Helobiales, and controverts the idea that they are a 

 reduced type. That they were more abundantly displayed dur- 

 ing the Cretaceous than now is evidenced by the fact that the 

 majority of our present genera were represented, and at least 

 three extinct genera have been detected. 



The above families would be expected by a morphologist to 

 occur among the earliest Monocotyledons, but the Cretaceous 

 record also discloses the presence of the Liliaceae. However, 

 they are comparatively few in number, occur in the upper mem- 

 bers of the Cretaceous series, and do not fairly display them- 

 selves until the Tertiary, when numerous and now extinct gen- 

 era appeared. These earlier liliaceous forms are of the Smilax 

 type, but this negative evidence is very uncertain, as this type 

 is peculiarly favorable for preservation. 



The Dioscoreaceae also appeared along with the Liliaceae, 

 and are so confused with the Smilax forms as to be difficult 

 to disentangle. 



The sixth family, whose existence during the Cretaceous is 

 possible but far from certain, is the Araeeae, to which certain 

 doubtful forms have been referred. Tt may have been scantily 

 represented, and its association with the Potamogetonaceae 

 would be confirmatory of Engler's suggestion as to their genetic 

 connection. 



