342 PROCEEDINGS OF THE 



the eye, the head showing the brain and a mount showing what 

 Dr. Leeson considered to be a sense organ. This was found on 

 the coxa ; it was an oval organ, with six or seven white spots, 

 upon it, each bearing two hairs. He had not been able to find 

 a notice of it in any book, although it was a very singular and 

 definite structure. A hearty vote of thanks was accorded to 

 Dr. Leeson. 



The President then gave an address on '' Colour in Plants and 

 its Preservation." The following is a condensed report of the 

 paper. It was stated that the object of the communication was 

 to show some of the results of attempts to preserve the colour 

 of plants in specimens destined for exhibition and to indicate 

 some methods with their possibilities and limitations. But it 

 would be helpful, first, to consider the substances with which 

 it would be necessary to deal. The colour of an object depends 

 on the quality of the rays of light which it reflects to the eye. 

 If no light is reflected it will appear black ; if all the rays which 

 make up white light are reflected it appears white ; and if only 

 a portion of the rays are reflected — others being absorbed — it 

 will have the colour corresponding to the rays which are re- 

 flected. Colour in plants is due to the presence of solid bodies 

 or solutions, which exercise a selective power on the rays of 

 white light which fall upon them. The solid bodies are special- 

 ised portions of the protoplasm ; at first white. On exposure 

 to light they develop a green pigment, chlorophyll, and are 

 known as chloroplasts. Later, by the formation of new pig- 

 ments, they may become yellow, orange or red, when they are 

 known as chromoplasts. The most important and widespread, 

 however, is the chloroplast, wliicli gives the green colour to the 

 leaves and young parts of the higher plants, and to the plant 

 body, or thallus, of the lower plants, algae and liverworts. In 

 the brown and red seaweeds it is masked by the presence of 

 other colouring matters. The green colour may be extracted 

 by alcohol. If the crude extract be shaken up with benzene, 

 a blue-gi'een dye is dissolved out, leaving behind a yellow 

 dye. Chlorophyll is an exceedingly complicated substance, in 

 the composition of which lecithins and possibly proteid com- 

 pounds take part. Most yellow, orange-yellow and orange-red 

 flowers owe their colour to chromoplasts. The pigment may be 

 uniformly distributed, but generally occurs as small amorphous 



