203 



HARDWICKE'S SCIENCE-GOSSIP, 



NOTES ON THE MOVEMENT OF THE 

 POLLINIA OF ORCHIS MASCULA. 



MR. E. MALAN, in his interesting paper in the 

 May number of Science-Gossip, on the 

 Fertilisation of Orchis mascula, replying to some 

 remarks made by a previous correspondent, infers, if 

 I read aright, that the form of the pollinium probably 

 has something to do with its movement, and suggests 

 an experiment with "a roll of moist clay." 



There appears to me to be an insuperable difficulty 

 in accepting this theory as an explanation of the move- 

 ment of the pollinia. The change of position is 

 uniformly in one direction, and this notwithstanding 

 that a pollinium may be held in such a position as to 

 cause the direction of movement to be against 

 gravity. 



An additional proof that the overhanging weight 

 of the pollinium has nothing to do with its movement 

 may be tested by a simple experiment. Remove 

 with a pair of forceps one of the organs in question, 

 without touching the viscid disc, or allowing it to 

 come into contact with anything ; carefully observe 

 it under the microscope, while still held quite free ; 

 the disc will be seen to move through a similar arc, 

 and in the same direction as it would have caused the 

 •caudicle to sweep had the disc been attached to 

 anything, thus showing weight and form are not 

 factors in the sense inferred by Mr. Malan. 



That the drying of the viscid disc is the cause of 

 the movement there can, I presume, be little doubt ; 

 the following experiments were made with the view 

 of satisfying myself on this point. Selecting properly 

 matured flowers, I removed a pollinium with a pair 

 of forceps as before described. I immersed the basal 

 portion in glycerine, and fixed it steadily under the 

 microscope ; after many hours' observation no visible 

 movement of parts had taken place. Proceeding in 

 the same way with water, I found the function, 

 though arrested for a time, was afterwards performed 

 when the water had evaporated ; substituting benzine 

 there was little, if any, delay in the movement as 

 compared with a pollinium in its natural condition. 



Immersing a pollinium in glycerine diluted with 

 water on a slip of glass, a very curious phenomenon 

 was observed. Tiny viscid globules and vermicular 

 threads of same were ejected from the cells of the 

 disc with some energy, resembling a miniature bom- 

 bardment of particles, the general appearance being 

 similar to the action of evaporating spirit when 

 viewed under the microscope. A globule or thread 

 after being emitted would frequently remain station- 

 ary for a second or two ; it would then dart off with a 

 Tapid motion, as though propelled by an explosive 

 force operating in the region of the disc. 



The action was the same when water only was 

 used. 



In both cases I did not observe any subsequent 

 movement in the parts of the pollinium. Substituting 



benzine, the emission was exceedingly feeble in some 

 cases, in others I altogether failed to detect it, while 

 on evaporation taking place the natural movement 

 again set in. 



With pure glycerine there was no emission, the 

 disc became quite transparent in a very short time, 

 but on adding a little water the action instantly 

 commenced, the globules being ejected as before 

 described. 



The movement of the pollinia may to some extent, 

 if not entirely, be due to the chemical qualities of the 

 contents of the cells of the disc ; the cause of move- 

 ment is undoubtedly due to the rapid contraction of 

 the cellular tissue caused by drying. The speedy 

 evaporation may be induced by the contents of the 

 cells being of a volatile character, as indicated by the 

 experiment ; but on this point I should prefer the 

 judgment of others more competent to speak than 

 myself. 



Mr. Malan will not, I hope, think these remarks 

 are made in a controversial spirit, but simply with the 

 view of contributing a mite towards solving a question 

 in the economy of a flower which is at once as 

 interesting as it is beautiful. 



W. H. Harris. 



Cardiff. x 



SCIENCE-GOSSIP. 



West Sussex Natural History Society. — A 

 very agreeable soiree was held by this Society on 

 June 9th at Chichester, in the lecture room of the 

 Museum. A prominent feature in the exhibition of 

 natural objects was that of about 200 species of living 

 wild flowers. Some excellent diagrams were dis- 

 played, and many interesting microscopical objects 

 shown. 



It appears from Dr. Perkin's presidential address 

 to the Society of Chemical Industry, as reported in 

 "Nature," that derivatives of quinoline as substitutes 

 for quinine have been prepared from coal-tar. Though 

 the artificial formation of quinine itself has not yet 

 been discovered, nevertheless other bodies have been 

 formed which are thought to have medical value, and 

 it is pointed out as an interesting fact that the coal- 

 tar colour industry itself had its origin in the attempt 

 to form quinine artificially. 



" Science" says that during the last twenty years 

 Swiss glaciers have shrunk in size, melting away up- 

 hill and retreating as much as a thousand feet or more 

 from their fresh-looking moraines. Of late, however, 

 it adds, not only has the retreat in many cases ceased, 

 but an advance has taken place during the last two or 

 three years. A map showing the recession of the 

 glacier of the Rhone during some years past may be 

 found in the same number of " Science." 



