232 Geological Society, 



entirely to the Lower Headon Beds, and consist of freshwater 

 and brackish-water (more ,or less calcareous) deposits, laid down 

 apparently in wide shallow lakes and lagoons. Such habitats are 

 the most favourable to the growth of Characeae, and several of the 

 beds have yielded numerous remains of these plants. 



There is a great diversity in the fruits of Chara found, repre- 

 senting evidently a number of species, belonging to several different 

 sections or genera. AVith the exception of a few, which are possibly 

 abnormal A^ariations, the fruits can be roughly grouped under the 

 following eight types : — 



I. Tuberculate series. (Type of C. tuherculata 'Ljell=Kosmogyra Staclie, 

 emend.) 



(a) Spherical. 



(b) Obovoid or pyriform, with distinctly prolonged base. 



II. Non-tuberculate series. 



(c) Large spherical, diam. c. 1 mm. (type of C. medicaginula Brongn.). 



(d) Large ellipsoidal (type of C. helicteres Brongn.). 



(e) Medium-sized, subglobose, tapering more or less at both ends. 

 (/) CyKndric-ellipsoidal, shoeing more numerous strijB. 



{(/) More or less pyriform : that is, definitely tapering towards the 



base. 

 (h) Minute, subglobose-ovoid (long.=c. 350 to 500 /i). 



It is difficult to determine the exact number of species found, 

 on account of the extreme variability of some of the forms, but 

 the Authors consider that at least twelve may, for the present, be 

 conveniently treated as distinct. 



The vegetative remains ai'e comparatively few, consisting of 

 minute portions of stems and branchlets of different diameters, 

 and these it is impossible at present to connect with an}^ particular 

 tj'pes of fruit. 



Though investigations of some earlier formations have shown 

 that there are extinct forms of Characese exhibiting important 

 points of difference from their living representatives, the remark- 

 ably distinct and characteristic oogonium of five elongated spirally- 

 twisted cells has remained constant certainly as far back as the 

 Inferior Oolite, and it is only in earlier formations that any doubt 

 arises as to whether bodies are or are not Chara fruits. 



Characea? are found in still fresh or brackish water all over the 

 world, under widely different conditions as regards heat, etc., and 

 may therefore be expected to occur in almost all freshwater 

 formations. For these reasons it is suggested that the fruits of this 

 group of plants, when more Avidely collected, may prove of consider- 

 able value as zonal fossils for the correlation of lacustrine deposits 

 lying in isolated basins. Doubtless, on account of their small size, 

 the Cliaraceae have in the past often been overlooked. 



