4 BRITISH CHAROPHYTA. 



and observing : " tliey are so different from all other 

 classes of plants that they must be erected into a 

 special group by the side of the Thallophytes and 

 Muscineae. Among the Thallophytes they would 

 approach most nearly to certain groups of Algse, but 

 differ from all the members of that group in the form 

 of their antherozoids ; and in this respect resemble 

 the Muscinese from which again they differ entirely in 

 the structure of the antheridia and of the female 

 organs of reproduction, as well as in that of their 

 organs of vegetation." (First Engl. ed. of ' Text-book/ 

 '18.75, p. 278.) 



In addition to the very distinctive character of both 

 antheridia and oogonia, and the absence of any clear 

 indication of aflinity with other existing groups of 

 plants, there is the fact that the form of the oogonium, 

 which is unlike the ' fruit ' of any other plant, has per- 

 sisted unaltered from certainly as far back as Oolitic 

 times. Their comparatively simple vegetative system 

 is probably due to the fact that they grow completely 

 submerged in still or evenly-running water, so that 

 they are exposed to little strain, or variation in 

 external conditions, and we do not think this should be 

 regarded as evidence of a low rank in the scale, in 

 view of the remarkably complicated structure of the 

 reproductive organs, especially the antheridium. We 

 follow Sachs in regarding the Charophyta as a 

 separate division. 



That the Charophytes represent a very 

 ancient type of vegetation is demon- 

 strated by the existence of fossil remains which un- 

 doubtedly belong to the group in the Lower Oolite,, 

 while organisms thought by some palgeontologists tO' 

 belong to ancestral forms, have been obtained from the 



