Microthamniacece 



89 



7*7 /x and of the erect branches only 1-5 1*8 /*. The plants bear considerable 

 resemblance to Herposteiron Nag. (Aphanochoete A. Br.) but differ in the 

 possession of completely septate branches instead of simple empty bristles. 

 The only other species of the genus is P. crassisetum West & G. S. West 

 which has been found in Ceylon, but it is quite possible that this is merely a 

 developmental stage of an epiphytic Myxonema. 



Genus Thamniochaete Gay, 1893 1 . The plants of this genus 

 are exceedingly minute, consisting only of three 

 to six cells. They are epiphytic and the basal 

 cell is usually modified to form a hapteron. 

 The terminal cell possesses an elongated bristle 

 or a short spine-like projection. The chloro- 

 plast is parietal and contains one pyrenoid. 



Th. aculeata West & G. S. West is a rare plant 

 occurring as an epiphyte in the thallus of Gloeotrichia 

 natanfi. It is only known from Connemara in Ireland 

 and from the Hebrides in Scotland. The diameter of 

 the cells is from 5'5 13 //, and the terminal bristle is 

 short and very sharp, arising below the apex of a 

 swollen terminal cell (fig. 31 A and B). Th. Hubert 

 Gay is epiphytic on a species of Oscillatoria and is 

 only known from the neighbourhood of Montpellier in 

 France. 



This genus represents the simplest type of all the 

 Chsetophoraceae a type in which branching is practi- 

 cally absent. In Th. Hubert the terminal cells are 

 furnished with hollow bristles or hairs exactly as in 

 typical and complex Chaetophoracese. 



Fig. 31. Thamnio- 

 chcete aculeata West 

 & G. S. West. A, 

 from near Balallan, 

 Outer Hebrides ; B, 

 from Baheh Lough, 

 Galway, Ireland ( x 

 520). 



attenuated and are 

 many of the more 



Family 6. MICROTHAMNIACEJE. 



The thallus is filamentous, branched, and of small size. The 

 branches are never attenuated into hairs and the cells are some- 

 times moniliform or torulose. The chloroplast is a parietal plate 

 with one or many pyrenoids, or sometimes entirely without them. 



The zoogonidia are only produced in special swollen cells of 

 the thallus which are differentiated as zoogonidangia. Reproduc- 

 tion frequently takes place by akinetes. 



It is a small family and bears considerable resemblance to the 

 ChaBtophoracese, being distinguished by the absence of multi- 

 cellular hairs and by the restricted origin of the zoogonidia. It 



1 Gay in Bull. Soc. bot. France, torn, xl, 1893, p. clxxvii cum fig. xylogr. 2. 



