VI PJJOCEEDTNUS OF THE GEOLOGICAL SOClETi'. [vol. Ixxiil, 



December 20th, 1916. 



Dr. Alfred Harkek, F.K.S., President, 

 in the Chair. 



Tlie List of Donations to the Library was read. 



Marie C. Stopes, D.Sc., Ph.D., gave an account ol some 

 recent researches on Mesozoic 'Cj^cads' (Bennetti- 

 tales), dealing particularly with recently-discovered petrified 

 remains which reveal their cellular tissues in microscopic prepara- 

 tions. To make the significance of the various fossil forms clear, 

 the Lecturer first showed some lantern -slides of living Cj^'ads, and 

 then pointed out that it was in their external featvu-es and in their 

 vegetative anatomy only that the fossil ' Oycads ' were like the 

 living forms : the most im])ortant features, the reproductive organs, 

 differ profoundly in the two groups, and the fossils were funda- 

 mentally distinct, not only from the living Cycads, but from all 

 other living or fossil families. 



The fossils representing the grouj) that are most frequently 

 found are {a) trunks, generally more or less imperfect casts or 

 partial petrifactions, and sometimes excellent petrifactions pre- 

 serving anatomical details and cell- tissues ; [b) impressions of the 

 foliage. Not infrequent are the detached im])ressions of incomplete 

 ' flowers ' or cones, of one cohort (the Williamsonete), while 

 petrified fructifications are numerous in some of the well-petrified 

 trunks of the Beniiettitea?. The described species of the group 

 run into hundreds, but probably many of these duj^licate real 

 species, because the foliage, trunks, pith-casts, various portions of 

 the fructifications, etc., have often been separately found and 

 named. In very few cases have the different parts been correlated. 

 The species of the foliage are the most genei-ally known, as they 

 are the most readih^ recognized with the naked eye ; they have 

 been described under a variety of generic names. 



The. following table gives the proved, or probable, associated 

 parts of some members of the group : — 



Foliage. Trunk. Fructifications. 



Zanxites spp. Bennettites spp. Beiinettites spp. 



Zamite)> gigas. Attached, no separate Williamsonia gigas. 



name. 



Otozamites sp. Williamsonia spectahilis. 



Ptilo2>h ijllum pectinoides. Williamsonia whithiensis. 



Anomozamites minor. (Only slender branches Wielandiella angustifoUa. 



known, no name.) 



Tseniopteri>< rittata. WiUiamsoniella covonafa. 



The Lecturer exhibited uiicrophotographic slides of the stem 

 and leaf-base anatomy of the group, including some unpublished de- 

 tails of Betuictfifes majrimtis. The roots of the group ha\e hitherto 

 been entirelv uidi:no\vn, and a slide was exhibited for the first time 



