GEOLOGICAL HISTORY OF THE CHAROPHYTA. 85 



nodes of the stem preserved. The solitary instance 

 in which I have been able to make out stipulodes clearly 

 was in some chalcedonized rock of uncertain age from 

 Matabeleland, described by Mr. R. BuUen Newton (14). 

 Of the fruits it is often the outer part consisting of the 

 spiral-cells only which is preserved, but sometimes the 

 oospore is also present. The coronula is apparently 

 never preserved, no doubt because its cells do not 

 secrete lime. In one instance only have fruits been 

 found of the longitudinally flattened form charac- 

 teristic of the genus Nitella* In the Tertiary marls and 

 limestones this is to be accounted for by the fact that the 

 fruits of Nitella do not develop a lime-shell, but in the 

 cherts of earlier formations in which thin-waUed cells are 

 perfectly preserved, if plants with the flattened type of 

 fruit existed one would expect to find some trace of them. 



In most productive deposits more than one distinct 

 type of fruit, and often several, are present, so that it is 

 rarely possible to identify fruits and vegetative parts as 

 belonging to the same species. 



Very much still remains to be done in connexion with 

 the fossil remains of the Charophyta, and it is from the 

 siliceous rocks of Mesozoic and Palaeozoic eras that the 

 most important results are to be looked for. From the 

 remains of the Charophyta which have as yet been 

 found, there is no reason to suppose that they were ever 

 larger plants than at the present time. There are no 

 signs of an exuberant development like that exhibited 

 by the Palaeozoic Pteridophytes. Charophyte-remaius 

 are not often found in company with those of other 

 water-plants, from which it may be inferred that they 

 usually monopolized the pieces of water in which they 

 occurred, much as they do at the present time. 



The fact that the very specialized form of " fruit " 

 has remained practically unchanged, from Carboniferous 

 times to the present day, would seem to point to the 

 Charophyta representing an extremely ancient and 



* From a deposit near Moscow regarded as luterglacial. 



