348 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1918. 



about 2 feet long, and bearing at the summit slender peduncles 

 20-30 centimeters long, covered with spirally-arranged scale leaves, 

 and terminated with an ovulate receptacle bearing pedicillate seeds 

 similar to those of Cycadeoidea surrounded by bracts or sterile 

 sporophylls united proximad to form a disk or cup. No trace of 

 microsporophylls are certainly known in this species, although the 

 probabilities are that it was bisporangiate, in fact, certain staminate 

 disks have been referred to this species by various students. 



Naturally, a very large number of different species of William- 

 sonia have been described from a variety of Mesozoic horizons and 

 localities, but few of these show essential features or have been 

 exhaustively investigated. A very characteristic form (IF. virgin- 

 iensis) occurs in the Lower Cretaceous of Virginia and another in 

 the Upper Cretaceous of Delaware. 



Among the better-known forms are W. spectabills from the York- 

 shire Jurassic, which shows a funicular disk prolonged into linear 

 lanceolate microsporophylls bearing on their inner faces fertile 

 pinnae carrying reniform synangia. A central ovulate receptacle 

 is wanting. W. ivkitbiensis, also from the Yorkshire coast, is similar 

 to the preceding, but the fertile pinnae are reduced and the reniform 

 synangia are borne on either side of the midrib along the inner 

 face of the free part of the microsporophylls. Still another type 

 is W. mexica/na from the Lias of Southern Mexico in which the cup 

 is deeply campanulate with 10 short narrow free lobes bearing two 

 rows of lateral synangia. 



The only petrified Williamsonia known is the imperfectly pre- 

 served W. scotica from the Jurassic of Scotland, which shows hairy 

 bracts, no traces of microsporophylls, and a central receptacle con- 

 sisting of interseminal scales and pedicellate seeds exactly similar 

 to Cycadeoidea 



An interesting and more reduced type, whose affinities indicate the 

 survival to the middle Jurassic of the Wielandiella type, is one 

 made the basis of the genus Williamsoniella. If the various parts 

 are correctly correlated they show slender, frequently dichotomous 

 stems bearing scattered leaf scars and believed to have borne the 

 associated type of foliage known as Taeniopterls vittata. In the 

 stem forks are pedunculate bracteate fructifications consisting of a 

 whorl of cuneate microsporophylls bearing five to six sessile reniform 

 synangia on either side of the inner keel. Within the whorl of 

 microsporophylls a pyriform receptacle with a sterile crown is cov- 

 ered with small interseminal scales and short-stalked seeds like those 

 of Williamsonia and Cycadeoidea. 



Remarkably well-preserved fronds from Greenland and elsewhere 

 described as Cycadites have recently been shown to possess a double 

 midrib separated by a stomatal groove, and these forms have con- 



