JOTTINGS FROM THE BIOLOGICAL LABORATORY 

 OF SYDNEY UNIVERSITY. 



By William A. Haswell, M.A., B.Sc., 



Lecturer on Zoology and Comparative Anatomy. 



7. — Cutting Sections of Delicate Vegetable Structures. 



There is a difficulty in obtaining by the means ordinarily 

 recommended, without considerable pains and loss of time, a 

 number of fine sections of such delicate vegetable structures as 

 the prothallium of a fern, fronds of delicate seaweeds, or thin and 

 flexible leaves of land plants ; and the following method which I 

 have found of service will recommend itself by its simplicity. 



The specimens to be cut, if they have been in alcohol, are 

 placed in water for a few hours, and then for a day in a thick 

 solution of gum arabic ; if fresh they may be placed at once in 

 the gum. Small pieces of carrot are placed in the gum for the 

 same length of time. ,^The specimens [to be cut and the carrot 

 which is to form the embedding material are now thoroughly 

 saturated with strong gum solution. Slits are made in the pieces 

 of carrot and the thin structures to be cut are inserted in the 

 slits, any interstices being frilled up with the gum. The 

 blocks of carrot, with the embedded specimens, are then frozen 

 and cut in the usual manner with the Freezing Microtome. 

 When the sections are placed in water there is little difficulty in 

 picking out the sections of the embedded objects from the light- 

 coloured and flocculent sections of the carrot — an operation which 

 is facilitated by agitation of the water, when most of the narrow 

 needle-like sections of the thin objects will find their way to the 

 bottom of the vessel. 



8. — " Vocal organs " of the Cicada. 

 It is a very prevalent idea, and the error is repeated in nearly 

 every manual of Zoology, that the Cicada's organ of voice is a 

 wind instrument. That such could not be the case, however, a 



