206 The Palaeontologkal Record. II Plants 



leaves give the Cycads a superficial resemblance in habit to Palms. 

 Recent Cycads are dioecious ; throughout the family the male fructifi- 

 cation is in the form of a cone, each scale of the cone representing 

 a stamen, and bearing on its lower surface numerous pollen-sacs, 

 grouped in sori like the sporangia of Ferns. In all the genera, except 

 Cycas itself, the female fructifications are likewise cones, each carpel 

 bearing two ovules on its margin. In Cycas, however, no female 

 cone is produced, but the leaf-like carpels, bearing from two to six 

 ovules each, are borne directly on the main stem of the plant in 

 rosettes alternating with those of the ordinary leaves — the most 

 primitive arrangement known in any living seed-plant. The whole 

 Order is relatively primitive, as shown most strikingly in its crypto- 

 gamic mode of fertilisation, by means of spermatozoids, which it shares 

 with the maidenhair tree alone, among recent seed-plants. 



In all the older Mesozoic rocks, from the Trias to the Lower 

 Cretaceous, plants of the Cycad class (Cycadophyta, to use Nathorst's 

 comprehensive name) are extraordinarily abundant in all parts of the 

 world ; in fact they were almost as prominent in the flora of those 

 ages as the Dicotyledons are in that of our own day. In habit 

 and to a great extent in anatomy, the Mesozoic Cycadophyta for the 

 most part much resemble the recent Cycadaceae. But, strange to 

 say, it is only in the rarest cases that the fructification has proved 

 to be of the simple type characteristic of the recent family ; the vast 

 majority of the abundant fertile specimens yielded by the Mesozoic 

 rocks possess a type of reproductive apparatus far more elaborate 

 than anything known in Cycadaceae or other Gymnosperms. The 

 predominant Mesozoic family, characterised by this advanced repro- 

 ductive organisation, is known as the Bennettiteae ; in habit these 

 plants resembled the more stunted Cycads of the recent flora, but 

 differed from them in the presence of numerous lateral fructifi- 

 cations, like large buds, borne on the stem among the crowded bases 

 of the leaves. The organisation of these fructifications was first 

 worked out on European specimens by Carruthers, Solms-Laubach, 

 Lignier and others, but these observers had only more or less ripe 

 fruits to deal with; the complete structure of the flower has only 

 been elucidated within the last few years by the researches of 

 Wieland on the magnificent American material, derived from the 

 Upper Jurassic and Lower Cretaceous beds of Maryland, Dakota and 

 Wyoming 1 . The word "flower" is used deliberately, for reasons 

 which will be apparent from the following brief description, based 

 on Wieland's observations. 



The fructification is attached to the stem by a thick stalk, 

 which, in its upper part, bears a large number of spirally arranged 



1 G. K. Wieland, American Fossil Cycads, Carnegie Institution, Washington, 1906. 



