2146 A TEXTBOOK OF THEORETICAL BOTANY 



I. Ascolichenes 2. Graphidineae 



a. Pyrenocarpeae 3. Cyclocarpineae 



'^. Gymnocarpeae \\ Hymenolichenes 



I. Coniocarpineae 



This system has received wide acceptance and was followed by Lorrain 

 Smith in her monograph of the Lichens, pubHshed by the British Museum 

 in 1 92 1. The systematics of the Lichens have been further revised in 

 detail by Zahlbriickner in the second edition of Engler's " Pflanzen- 

 familien", published in 1926, but he has made no fundamental change in 

 his original method. 



THE CHAROPHYTA 



The Charophyta have had a chequered career so far as their systematic 

 position is concerned, due mainly to the fact that their reproductive organs 

 for long remained a botanical puzzle. The difficulty lies in the marked 

 diiferences which they exhibit from any other known living types. Early 

 writers grouped the Charophyta either with the genus Equisetum or with 

 Hippuris on account of their superficial resemblance to these plants. Later 

 the group was variously included in the Naiadaceae, in the Bryophyta, 

 in the Vascular Cryptogams and finally in the Algae. 



Strasburger placed them in a separate class of the Thallophyta, while 

 Sachs separated them as a phylum, the Charophyta, equal in rank with the 

 Thallophyta. Modern tendencies have been to transfer them to the Algae. 

 Oltmanns treated them as a separate group of the Algae, equal in rank with 

 the Chlorophyceae, while Fritsch in his later work includes them in the 

 Chlorophyceae. 



The most comprehensive treatment of the group was that written by 

 Braun and published in Rabenhorst's " Kryptogamenflora " between 

 1877 and 1879. The only modern treatment in English is due to Grove and 

 Bullock Webster, who between 1920 and 1924 published two volumes 

 illustrating all the British species under the title of " The British Charo- 

 phyta". In this they follow the same system of classification as Braun, 

 which we may summarize as follows: 



1. Nitelleae. Including the genera Nitella and Tolvpe/la. 



2. Chareae. Including the genera Nite/lopsis, Lamprothamnion and 



Chara. 



Fossil evidence indicates that the group is of great antiquity. It will 

 probably remain a matter of opinion whether the peculiarities of their 

 reproductive organs and their high degree of thallus specialization do, or 

 do not, justify the separation of the Charophyta into a separate phylum. 



