Feb. 1891.] BOTANICAL SOCIETY OF EDINBURGH. 55 



shown is one made by Messrs Watson & Son of London, on 

 the plan adopted by Zeiss of Jena, and now universally used 

 in the construction of iris diaphragms by all opticians. 

 The mechanism for working the plates requires a less breadtli 

 of surrounding ring, and therefore occupies less space than 

 formerly, and when the plates are about a dozen or more in 

 number, the aperture is about a perfect circle. No first- 

 class microscope is now made without an iris, which is the 

 most perfect and rapid microscope shutter made. The ring 

 is so narrow that various makers now put them inside the 

 mounts of photographic lenses, only the end of the lever 

 being outside the tube. They are also placed by some 

 makers, such as Messrs Cooke of York, in front of large 

 telescope objectives to enable the observer to reduce the 

 aperture when required. The iris is one of these small time- 

 saving accessories to an instrument which those who once 

 have experienced its use would not readily do without. 



Mr E. M. Holmes sent for exhibition specimens of Geaster 

 striatus, D.C., and wrote : — The plant was met with near 

 Sevenoaks, in Kent, in October, growing among the stems of 

 a hazel bush which had been cut down on a bank in front of 

 a hedge. The hedge had been trimmed, and the bushes on 

 the level bank (about a yard across) had been cut close to 

 the ground. The Geaster looked so like scattered chips of 

 hazel bark which were lying with it, that had it not been for 

 the nearly globular inner peridium I should not have noticed 

 the plant. I mention these details to show how easily a 

 plant, considered rare, might not really be so rare as is sup- 

 posed, but might be overlooked. In all the plants, even the 

 smallest that I saw, the outer peridium was already expanded, 

 and the point of attachment to the ground not visible, on 

 account of the recurved segments having raised the plant 

 from the ground. Geaster striatus is reported from Yarmouth, 

 and as growing among sand. The soil in the lane where the 

 plant grew at Sevenoaks is a sandy loam on greensand 

 formation. The species resemble G. limbatus, Fr., but differs 

 in the mouth being prominent, conical and sulcato-striate, 

 instead of depressed and fimbriato-pilose. In Geaster Bryantii 

 Berk., which also resembles it, there is a channel round the 

 top of the peduncle, which is not present in G. striates. 



