XXX V] CONOSTOMA 313 



Conostoma. Williamson. 



This name 1 , suggested by the funnel-like pollen-chamber or 

 lagenostome, was applied by Williamson 2 to some seeds from the 

 Lower Coal Measures of Lancashire and Yorkshire and from 

 the Lower Carboniferous beds of Burntisland. The Burntisland 

 seeds, referred by Williamson to two species, have recently been 

 united and described by Miss Benson as Sphaerostoma ovale 3 . 

 The English species has been thoroughly investigated by Oliver 

 and Salisbury 4 who have also described a second species, C. anglo- 

 germanicum, from the Coal Measures of Lancashire and Germany. 



Conostoma oblongum Williamson. 



This rare type is represented by approximately cylindrical seeds 

 with an average length of 5mm. and a maximum breadth of 2-3 mm. 

 borne on a relatively stout stalk and tapering to a blunt apex 

 characterised by a canopy of six short lobes (fig. 494, B, C) in 

 marked contrast to the long tentacles of PJiysostoma. In the basal 

 region the integument has six prominent ribs which soon die out 

 when traced upwards : a transverse section through the body of the 

 seed is hexagonal (fig. 494, D), the angles corresponding to the basal 

 ribs, and there is a slight tendency to platyspermy. The testa 

 has an epidermal mucilaginous layer which becomes exfoliated 

 through the lifting- up of the cuticle by the underlying mucilage: 

 below this, at the apex of the seed, is a cap of fleshy tissue (fig. 

 494, B, so) which, it is suggested, may have had a secretory 

 function in connexion with a drop-mechanism in pollination like 

 that in recent Conifers. No microspores have been found in the 

 pollen-chamber. The epidermis, called by Oliver and Salisbury 

 the blow-off layer (fig 494, B, m), together with the cap of soft 

 tissue constitute a feebly developed sarcotesta. A sclero testa 

 consisting of a palisade-layer and a fibrous hypoderm extends 

 over the main body of the seed below the epidermis ; it forms the 

 basal ribs and increases considerably in breadth at the apical 

 region to form a sclerous cone penetrated by six strands of 

 parenchyma enclosing vascular bundles (fig. 494, D) which pass 

 up from the conducting tissue immediately external to the nucellus. 



a cone. 2 Williamson (77) B. p. 241, Pis. XL, xn. 



3 Page 79. * Oliver and Salisbury (11). 



