1498 



THALLOPHYTES. 



— consists of a large central cell surrounded by a sheath of spirally- 

 twisted cells, and bearing a crown of small teeth at its summit 

 (fig. 1365, s). 



The recent genus Nitella remains permanently soft, and is un- 

 known in the fossil condition. On the other hand, the integu- 

 ment of Chara itself becomes hardened by an encrustation of car- 

 bonate of lime, and is thus capable of preservation in the fossil 



state. The fossil forms of the genus 

 Chara occur in the Triassic, Juras- 

 sic, and Cretaceous formations, and 

 are abundant in parts of the Ter- 

 tiary series. In some cases (as in the 

 chert of the Purbeck beds) the stems 

 are found ; but the fruits or " carpo- 

 gonia " are more commonly preserved. 

 These have the form of spirally ridged 

 or grooved, ovoid or globular bodies 

 (fig. 1366), and the first type dis- 

 covered was described by Lamarck under the name of " Gyro- 

 gonites." The fossil carpogonia of species of Chara are abund- 

 antly found in certain freshwater deposits, both of Secondary and 

 of Tertiary age. 



Fungi. 



The series of the Fungi, in which the Lichens are now included, 

 comprises Thallophytes which are closely allied to the Algcs, but 

 which are devoid of chlorophyll. Owing to the soft nature of their 



Fig. 1366. — a, Carpogonium of Chara 

 Gressini, Tertiary, enlarged ; b, Carpo- 

 gonium of Chara Medicaginula (" Gy- 

 rogonites"), from the Eocene beds of 

 the Paris basin, enlarged. (After Schim- 

 per and Zittel.) 



Fig. 1367. — A, A lenticular specimen of Archagaricon, of the natural size; B, Slice of the same 

 showing the tubes and vesicles, enlarged. Coal-measures. (After Hancock and Atthey.) 



tissues, the Fungi can only be preserved in the fossil state under 

 specially favourable conditions. The plants of this series are, there- 

 fore, of very small palseontological importance, and may be very 

 briefly dismissed. 



