OF THE GENUS TRICHIA. 21 



same as the appearance in the TVicAza-threads. I have seen 

 on one occasion the membrane of a thread of T. pyrifornns 

 unrolled spirally in the manner represented in fig. 10, Plate 

 II. ; this circumstance is soinewhat curious, as membrane does 

 not ordinarily unrol in that manner, although it has been 

 observed by Professor Quekett to take place in the hairs of 

 the fruit of Cycas revoluta* I do not know that this fact has 

 any very strong bearing upon the question of structures ; but 

 if, as would seem to be the case from its greater transparency, 

 the elevated position of the cell- wall is thinner than the rest, 

 it is easy to imagine that a rupture of the wall would be likely 

 to take a spiral direction. 



The following is a list of the Tricliia hitherto recorded as 

 British, viz., Tricliia pyriformis, serotina, fallax, clavata, tur- 

 binata, chrysosperma, varia, Servula, Neesiana,^ and Ayresii ; 

 and to these must be added Tricliia niqripes^ which I met with 

 last autumn in the neighbourhood of Eltham in Kent. 



With regard to the preparation of the T/'/cAm-threads for 

 the microscope, there are many methods which may be used. 

 Owing perhaps to the dense crowding of the hairs, the getting 

 rid of air-bubbles is the principal difficulty. Alcohol is the 

 easiest medium to employ, and I have reason to think that the 

 colour of the threads is not affected by it, which is the only 

 thing which might be feared. Deane's gelatine is a very good 

 preservative, and may be used without difficulty if the threads 

 are previously left to soak for some hours in chloride of cal- 

 cium ; and castor oil answers admirably well, altliough when 

 this is used there is sometimes a little difficulty in fixing the 

 thin glass cover. In conclusion, I would venture to express a 

 hope that some of the readers of the Microscopical Journal 

 may be induced to direct their attention to the investigation of 

 these disputed threads ; iri'espective of the interesting question 

 of structure, the beauty of the objects will fully compensate 

 them for the trouble of examination. 



Observations on Aphanizomenon Flos-aqu^, and a species of 

 Peridinea. By G. J. Allman, M.D., Professor of Botany 

 in the University of Dublin. 



The substance of the following communication has already 

 appeared in the Proceedings of the Royal Irish Acadeiny ; 



* See Lectiires on Histology, p. 100. 



t Fries has expressed an opinion that Trichia Xeesiana is identical with 

 T. rubi/'ormis ; Bonorden, however, assei-ts, that in T. rubiformis there 

 is no spiral appearance. It" tliis be so, they cannot be identical ; for T. 

 Ncesiana sliows the spiral marking; more beautifully than any which \ 

 have examined. 



