108 



culus is not always present and in one specimen of mine (Nr. 

 1317) the mucronated assimilating cells were rare, nearly all had 

 a broadly rounded summit (Fig. 117). 



The specimens I have collected formed rather large and dense 

 tufts composed of numerous richly ramified branches. At the base 

 the main branches are terete or nearly so but higher up all the 

 branches become quite flattened. They are either repeatedly 

 forked or irregularly ramified (Fig. 115). 



The colour of the dried plant is greyish to olive-green with 

 a reddish tinge especially in the upper parts. The surface is dull 

 and when seen under a lens finely dotted, this appearance ori- 

 ginating from the closely placed but free assimilating cells. In 



this respect it differs from the Galaxaura 

 occidentalis, mentioned below, this having 

 a more even and often shiny surface while 

 both plants otherwise show a striking 

 remblance in their habit and where grow- 

 ing together. 



In the dried specimens the edges of 

 the branches are often somewhat pro- 

 minent giving the branches a chanelled 

 appearance. 



In my specimens the transverse stri- 

 ations were not much developed some- 

 times not at all; when present they 

 were mostly found towards the summit 

 of the branches (Fig. 115). 



With regard to the flattening of 



the branches some differences are present in the various speci- 

 mens. In some (my collection nr. 1317 a) a transverse section 

 of the thallus is nearly oval, while in others (nr. 1657 b) this 

 was oblong linear with quite parallel sides. In specimens pre- 

 served in spirit the branches are also clearly flattened (compare 

 the branch to the right in Fig. 115) but not as much as is the 

 case with the dried specimens ; their edges are rounded and they 

 show no trace of being channelled. 



A transverse section of the thallus shows that the medullary 

 tissue consists of irregularly, subdichotomously ramified filaments 

 running between each other in the mucilage found here; they 

 have rather thick walls and a diameter of about 14 ^, but both 

 thicker and thinner are present. Outwards these filaments bear 



Fig. 117. Galaxaura mar- 

 ginata (Sol.). Transverse 

 section of the periferic 

 tissue. (About 200 : 1). 



