BRITISH DESMIDIE.E. 143 



37. S. spinosum (Bieb.) ; segments elliptic, furnished with a few bifid 

 spines ; lateral spines solitary, larger and more forked ; end view 

 triangular with two or three spines on each side and one terminating 

 each angle. 



Staurastrum spinosum, Brebisson, iyi lit. cum icone (1847). 



Dolgelley and Penzance, /. R. Ambleside, Mr. Sidebotham. Reigate, 

 Surrey, Mr. Jenner. 



Falaise, Brebisson. 



Frond deeply consti-icted at the middle ; segments subelliptic, their outer 

 margin usually more turgid than the inner ; on each side is a conspicuous 

 sessile spine, forked like the tail of a swallow, and on the outer margin are a 

 few smaller spines, which are usually forked at the end, though sometimes 

 simple. End view triangular, each angle terminated by a spine, which ap- 

 pears simple or forked according to its position when viewed ; sides with two 

 or three spmes, which are sometimes simple and sometimes forked, and on the 

 upper surface are six other spines, one opposite to each lateral spine. 



The sporangia of Staurastrum spinosum were first gathered by Mr. Broome 

 near Bristol, and I have since found a few of them at Dolgelley. They are 

 orbicular, and have numerous elongated sprues which are divided at the apex. 



M. de Brebisson considers this plant identical with the Xanthidium fur- 

 catmn, Ehr. 



Length of frond gJ-g of an inch ; breadth 9^^; breadth at constriction -g-J^Y ; 



diameter of sporangium -^^ ; length of spine of sporangium yjW • 



Tab. XXII. fig. 8. a. front view of frond ; b. end view; c, d. sporangia. 



38. S. vestitum ; frond rough with minute emarginate spines; 



segments fusiform ; end view triradiate, each side having two 

 spines, short, slender, and often accompanied by other smaller ones. 



Dolgelley, J. R. Near Pulborough, Sussex, 3Ir. Jenner. 



Frond broader than long, about as large as that of Staurastrum gracile, 

 deeply constricted at the middle, the constriction formmg a triangular notch 

 on each side ; segments somewhat fusiform, turgid on the inner margin, 

 tapering at each side into a short process which is tipped by three or four 

 minute spines ; outer margin fringed with minute emarginate spines or tubercles. 

 End view triradiate, showing also two slender forked spines at the middle of 

 each side, whilst the margin is often fringed with other spines, which are 

 smaller and either simple or notched. The rays are elongate, rough with 

 minute granules, and terminated by minute subulate spines. 



In the end A^ew Staurastrum vestitum resembles S. gracile in figure, but 

 that species is not spinous. The rays in the end liew are more slender than 

 those of S. aculeatum or (S. controvei-sum : but the most distinctive character 

 of this species is the presence of a pair of slender forked spines at the middle 

 of each margin. 



