364 MISCELLANEOUS SEEDS [CH. 



Thysanotesta. Nathorst. 



Nathorst^ founded this genus on a single seed from the Lower 

 Carboniferous plant-beds of Spitzbergen which exhibits features 

 sufficiently distinctive to justify its recognition as the type of 

 a separate genus. 



Thysanotesta sagittula Nathorst. The type-specimen is a 

 long and narrow seed, 20 mm. long, ovate below and prolonged 

 apically into a slender beak, 8 mm. in length, which probably 

 represents a micropylar tube; the beak bears numerous stifE 

 hairs (fig. 506, F). The seed closely resembles a carpel of Erodium 

 without the horizontal part of the awn. There is no evidence 

 as to the nature of the parent-plant but the species affords an 

 interesting example of a Palaeozoic seed apparently adapted for 

 wind-dispersal, or possibly the bristles may have served the same 

 purpose as in the fruits of Erodium. Attention is called elsewhere* 

 to the frequent resemblance of Palaeozoic seeds such as Thysano- 

 testa to fruits of recent flowering plants. 



Carpolithus. Linnaeus. 



Nathorst* has pointed out that this generic name was employed 

 by Linnaeus for fossil fruits: in the form Carfolites (Sternberg) 

 or Carpolithes^ it has been widely used and differently defined 

 by authors, usually in a comprehensive sense including fossil 

 seeds from both Palaeozoic and Mesozoic strata which cannot be 

 assigned to a definite position in the plant-kingdom. It is desirable 

 to adopt some designation for seeds from strata of different ages 

 which do not exhibit any features sufficiently distinctive to justify 

 the creation of a special genus. By employing such a name as 

 Carpolithus, without attempting to define its characters within 

 prescribed Umits, for casts or impressions of seeds which are not 

 distinguished by any striking characters and cannot be allocated 

 to any particular section of seed-bearing plants the unnecessary 

 multiplication of generic titles is avoided: when any additional 

 data are obtained differentiating particular types from other forms 

 of Carpolithus the provisional term should be superseded by some 

 distinctive generic name. Among seeds from the Coal Measures 



1 Nathorat (14) p. 33. PL XV. figs. 69, 70. " See page 304. 



3 Nathorst (14) p. 33. « Seward (95) A. p. 101. 



