Camptotrichacece 



341 



old. The filaments radiate from the centre outwards, and, as in 

 Rivularia, exhibit a false 'branching.' The sheaths are only 

 conspicuous near the base of the trichomes, being gelatinous and 

 confluent near the periphery of the thallus. The trichomes are 

 strongly attenuated from the base, and are more or less torulose. 

 From the cell immediately above the basal heterocyst elongated 

 cylindrical spores are developed, which remain for some time 

 within the basal part of the sheath. 



There are two British freshwater species, G. Pisum (Ag.) Thur. and 

 G. natans (Hedw.) Rabenh. The former possesses a thallus which does not 

 reach a greater diameter than 2 mm., but the latter is a larger species with 

 a thallus up to 10 cms. diameter. G. Pisum is one of the Algae frequently 

 concerned in the phenomenon of the " breaking of the meres." 



Family 2. CAMPTOTRICHACE^S. 



This is a small family sharply marked off from the rest of the 

 Trichophoreae by the attenua- 

 tion of the filaments from the 

 middle towards each extremity. 

 The plants are epiphytic and 

 there are no heterocysts. The 

 sheath may be very thin and 

 delicate, or thick and lamellose. 

 Only two genera are known, one 

 of which (Camptothrix) is a genus 

 of small tropical epiphytes. 



.Genus Ammatoidea West & 

 G. S. West, 1897. The filaments 

 are epiphytic and exhibit a false 

 ramification comparable with that 

 met with in Rivularia. They are 

 suddenly bent in their median or 

 widest portion, the two more or 

 less parallel extremities being 

 gradually attenuated topiliferous 

 apices. The sheaths are firm and 

 lamellose, in young filaments 

 colourless, but in older ones of a 



yellow-brown colour. The tri- F >_ 15 J- Ammatoidea Normanii 

 J . . . W. & G. S. West, from Dartmoor, 



chomes exhibit a slight constric- Devonshire ( x 420). 



