﻿CHAPTER V. 

 FOLIAGE. 



(Plate xix.) 



It is generally held that cycadaceous plants culminated in the Jurassic ; and, in 

 fact, they seem to have been quite the most ubiquitous of seed-bearing plants through- 

 out all of Mesozoic time to the Upper Cretaceous. Even then they were still present 

 in the Arctic area, though as a fast-disappearing remnant already beginning its long 

 and gradual retreat toward present isothermal limits. Nevertheless the abundant 

 and widely distributed remains of this vegetation consist almost entirely in discon- 

 nected and isolated leaves, trunks, and occasional fruits, of necessity hitherto 

 described under separate generic and specific names. It seems that but very rarely 

 have conditions favored the preservation or detection of organically connected leaves 

 or fruits and stems of these plants. Indeed, among all the fossil remains from the 

 plant-bearing horizons of the globe of all ages, until recently, but a single well- 

 authenticated instance of a stem with leaves attached could be pointed out. As 

 early as 1834, however, Williamson (200) expressed the opinion that Zamites gigas 

 and Williamsonia were to be regarded as probably leaf and fruit of one and the same 

 plant. And by 1870, as the result of long and keen observation, this able paleo- 

 botanist was confirmed in his belief in the organic connection of the stems, leaves, 

 and fruits included at various times under the names Zamites and Williamsonia 

 gigas. The restoration of the plant bearing the latter name as given by Williamson 

 in 1870 (202), at first received the confirmation of Brongniart, and is now known 

 to be essentially correct, although it came to be for a long time regarded, particu- 

 larly by Saporta, as resting on insufficient fossil data. The opinion of the latter, 

 given in connection with his description of various Paris Museum specimens of the 

 James Yates collection from the Lower Oolites of Whitby, published in 1875, is 

 very interesting. For in giving his views, Saporta (125, p. 55) not only rejects 

 the organic connection of the stems, leaves, and fruits of "Zamia gigas" as unlikely, 

 but calls in question the affinities of the fruits as follows: "C'est une certaine con- 

 formity apparente entre les appareils floraux auxquels on peut laisser le nom de 

 Williamsonia et le Zamites gigas tel que le fait voir la remarquable empreinte de la 

 collection du Museum de Paris (Voy., PI. 81, fig. 1). Nous avons tout lieu de con- 

 sider les Williamsonia comrne repr£sentant l'inflorescence d'une monocotylddone 

 primitive, revelant un type de Pandanees plus ou moins analogue aux Yucciles, aux 

 Podocarya, aux Eolirion de Andrae, etc." Saporta's view was, at least in so far as 

 the independence of the fossils in question was concerned, rather widely held for a 

 time, Nathorst (100) having even tentatively suggested a relationship between 

 Williamsonia and the parasitic broom-rapes so remarkably developed in tropical 

 regions. 



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