XXXV] CONOSTOMA 313 



Conostoma. Williamson. 



This name^, suggested by the funnel-Uke pollen-chamber or 

 lagenostome, was applied by Williamson^ 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 WilHamson to two species, have recently been 

 united and described by Miss Benson as Sjphaerostoma ovale^. 

 The Bnghsh species has been thoroughly investigated by Ohver 

 and Sahsbury* who have also described a second species, C. anglo- 

 germanicum, from the Coal Measures of Lancashire and Germany. 



Conostoma oblongum Wilhamson. 



This rare type is represented by approximately cyhndrical seeds 

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

 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 Physostoma. 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 sUght tendency to platyspermy. The testa 

 has an epidermal mucilaginous layer which becomes exfoUated 

 through the hfting-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, sa) which, it is suggested, may have had a secretory 

 function in connexion with a drop-mechanism in polUnation hke 

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

 pollen-chamber. The epidermis, called by OHver and Sahsbury 

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

 tissue constitute a feebly developed sarcotesta. A sclerotesta 

 consisting of a pahsade-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. 



1 K(ivos, a cone. ' Williainson (77) B. p. 241, Pis. xi., xii. 



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



