CYCADEAE, MEDULLOSEAE. 87 



casts of detached seeds, which from their size and shape may properly be 

 considered as Cycas-seeds (Cycadeospermum hettangense, Sap.). And if 

 we are anywhere justified in concluding that parts belong to one another 

 because they are found lying together in the same place, we are so here, 

 where the consideration of the whole of the circumstances leads almost of 

 necessity to the same conclusion. 



But in the case of all other remains of Cycads from the prehistoric 

 world we have no grounds for concluding that they are affiliated to living 

 forms. Here therefore we can only adopt confessedly artificial genera for 

 the stems, leaves and remains of flowers, and arrange our material in these 

 according to such external characters as we can recognise in it. In dealing 

 with the leaves which have first to be considered, it is unfortunate that they 

 do not of themselves enable us to distinguish between Ferns and Cycads 

 with absolute certainty. Neither the shape of the expanded part, nor the 

 course of the nerves, nor the form of the epidermal cells can decide the 

 question. It is true that the epidermal cells are usually polygonal with 

 straight side-walls in Cycads and with arcuately curved walls in Ferns, but 

 the genus Stangeria agrees with the Ferns in this respect and was originally 

 described by Hooker as Lomaria. Schenk therefore, who like Borne- 

 mann 1 attempted to determine the nature of the leaves from this character 2 , 

 has since ceased to employ it 3 . The structure of the vascular bundles 

 might possibly have supplied a certain criterion, but this is unknown, as 

 there are no petrified specimens ; the only resource left us is the habit, 

 and this, as the case of Stangeria sufficiently shows, may mislead us. 'Since 

 the determination of all these remains rests on so insecure a foundation, we 

 cannot be surprised that some of them have been shifted backwards and 

 forwards by different authors from Cycads to Ferns and from Ferns to 

 Cycads. Of such forms it will be well to select the genus Otozamites, Fr. 

 Braun (Otopteris, Ldl. and Hutt.) for consideration in this place, and to 

 discuss a number of others, Noggerathia, Sternbg, Thinnfeldia, Ettingsh., 

 Dichopteris, Zigno, Cycadopteris, Zigno, Nilssonia, Brongn., later on with 

 the Ferns. 



Older authors, like Brongniart 4 , were content with a few genera for the 

 reception of their fossil forms. As the value of these genera was purely con- 

 ventional, this was wisely done. The later multiplication of genera, in which 

 great weight was attached to details of character, has become the fruitful 

 source of endless synonymy and transference of species, and thus the general 

 view has been obscured, while little has been gained in the way of deeper in- 

 sight into the nature of the remains. A full description of all these genera, 

 which have little interest for the botanist, is to be found in Schimper 5 . A few 

 remarks founded on Brongniart's observations may be sufficient in this place. 



1 Bornemann (1). 2 Schenk (3) 3 Schenk (1). ' Brongniart (2). 5 Schimper (1). 



