458 



41. S. INTESTINALIS. 



[CL. XXIV. 



41. 



Scythosiphon intestiiialis, Lyngh. 



In summer, there appear upon our running and stagnant 

 waters, yellowish-green, membranaceous, spongy tubes, which 

 frequently cover a large surface of the v/ater. When young 

 they are filiform, and of a bright green. These threads are 

 firmly attached to stones with a shield-shaped expansion, and 

 ascend as tubes, which gradually become wider, but are con- 

 tracted in particular places, without exhibiting any partitions, 

 and swim on the water, where they are then filled with water, 

 and throw up air-bubbles. When in their perfect state, they 

 resemble the intestines, and are about the thickness of a fin- 

 ger : towards harvest they always become discoloured, more 

 yellow, and finally dissolve into slimy matter. When we 

 examine the fine sides of the tubes with a microscope, we 

 observe fine grains collected together in fours. 



Diagnosis; and Affinity. 



The species which stands nearest to this is Sc, compressus 

 Lyngb., but this latter plant grows only in salt water, is 

 branched and compressed, and is not so thick as Sc. intes^ 

 tinalis. Formerly both of these were arranged under Ulva ; 

 but Roth remarked (Catal. 1. 158.), that the definition of 

 Ulva includes the level, expanded, but not tubular nature of 

 the frond. Hence he classed the Ulva intestinalis with the 

 Confervae ; but the latter has always jointed tubes, and these 

 furnished with partitions. Hence Lyngbye very properly 

 formed the genus Scytosiphon^ the character of which consists 

 in its membranaceous, uninterrupted tubes, the seeds of 

 which contain the granular germs. 



