270 



HARDWICKE'S SCIENCE-GOSSIP. 



the assistance of that relief granted by binocular j 

 vision. 



Wenham's new arrangement produces some 

 stereoscopic effect iu the mind of the observer by 

 the mere fact of binocular vision, and this is so 

 decided, that many who have seen it declared it to 

 be stereoscopic. This new combination of prisms 

 performs equally well with all powers from a half- 

 inch to tbe one-fiftieth of an inch inclusive ; but 

 with low powers, for which it is not designed, the 

 effort is painfully flat to those accustomed to the 

 splendid stereoscopic effect of the Wenham low- 

 power prism. 



As I have seen the markings in Surirella gemma, 

 Navicula rhombdides, Navicula crassinervis, Frus- 

 tulia Saxonica, &c, distinctly in the supplementary 

 body, I cannot but pronounce the reflection of this 

 new arrangement to be almost perfect. Of course 

 there is a slight difference in the brightness of the 

 images of the direct and the supplementary body ; 

 but as the left eye is generally more sensitive to the 

 effects of light, this difference in brightness is not 

 felt. The more powerful the light, the more the 

 two fields are equally illuminated. Using that ne 

 plus ultra of a microscope lamp— the Dallinger 

 Lamp, a most useful accessory, which has a wick 

 \\ inch broad,— the difference in brightness of the 

 two fields is scarcely perceptible, and with sunlight 

 modified it disappears altogether. 



I exhibited this new arrangement at the conver- 

 sazione given by the Philosophical Society of 

 Glasgow to the members of the British Association 

 on 7th September last ; and although I showed the 

 cyclosis in so opaque an object as the leaf of Ana- 

 charis alsinastrum, under the one-fifteenth objective, 

 using a lamp having a wick only half an inch broad, 

 all those who saw it will grant that the performance 

 left nothing to be desired. 



I hope that the time has come when no optician 

 will send out a binocular- stand without having a 

 binocular arrangement for the highest powers. 

 Messrs. Ross & Co., I believe, have not advertised 

 these new high-power binocular prisms, for fear of 

 creating a demand which they would have the 

 greatest difficulty to supply; but I trust that they 

 will at once make arrangements to produce them on 

 a larger scale, so that the comfort and luxury of 

 binocular vision under the highest powers may no 

 longer be denied to those who have to do without it 

 in the mean time. By the withdrawal of the 

 prisms the microscope is instantly converted into a 

 monocular one. ! Adolf Schtjlz. 



"Trohcal Africa and Southern Asia (and 

 Lenmria) are those portions of the earth which 

 deserve the first consideration in the discussion 

 as to the primeval home of the human race." — 

 Haeckel's " History of Creation." 



THE MISTLETOE AND ITS ASSOCIATIONS. 



THE oldest specimen of mistletoe I have seen 

 noticed is that mentioned in Science-Gossip, 

 April, which " appears to be about fifteen years 

 old." Are there any recorded instances of the 

 plant living to a greater age than this ? We can 

 hardly suppose this is the oldest. In the Kew 

 Museum are specimens of apple-tree, &c, in which 

 the parasites having died and decayed " before the 

 stock upon which they grow, and have left curiously- 

 furrowed moulds or casts answering to the space 

 occupied by their attachment." Have any fossil 

 vegetable parasites been yet discovered ? It is not 

 probable that they have appeared during the pre- 

 sent era. To what age do the leaves live ? The 

 shrub is evergreen, but the leaves may be only 

 annual. Hooker, in his " Students' Flora," gives the 

 geographical distribution of this plaut thus^:— 

 " Europe, N. Asia." It is said not to be a native of 

 Scotland, Ireland, or the Channel Isles. In all 

 these places Druidical remains are frequent, and 

 from Ireland, at least, the Druids would be unable 

 to attend the great annual meeting at Avalon, and 

 would have to conduct their New Year's cere- 

 monies themselves. How did they do this without the 

 mistletoe, or must we suppose that it has become 

 locally extinct since that time ? In the "London 

 Catalogue " it is mentioned that it is found only iu 

 thirty-eight of the 112 botanical counties into which 

 Great Britain is divided. The allied species, Loranthiis 

 Europceus — whose frequent habitat is the oak, and 

 which is considered by some to be the true plant 

 venerated by the Druids,— is said to be plentiful iu 

 all European countries in which the Druidic religion 

 has not been prevalent, and to have been exter- 

 minated elsewhere. Does this plant extend to the 

 snow-line on the mountains and plains, or how near 

 does it approach it ? What are the largest plants 

 on record ? 



I have been unable to find sufficient chemical 

 analyses of this plant to make their comparison 

 interesting. It would be very interesting to inquire 

 whether the ash varies in plants taken from the 

 same support in different localities, and from 

 different ones in the same locality. We should 

 probably find some instructive differences in the 

 constituents of the ash. I can only add to the lists 

 of support plants already given in SciENCE-Gossir 

 three fresh names. In Hooper's "Medical Dic- 

 tionary " the hornbeam (Carpiiuts betulus) is given 

 as an occasional habitat; iu another work the 

 sycamore is given ( ? Acer pseudoplatanus) ; and iu 

 Decaisne and Le Maout's " General System of 

 Botany" it is mentioned that it even attaches itself 

 to Loranthus Europceus, which is itself parasitic 

 upon oaks ! Iu two or three works the mountain 

 ash is mentioned as a habitat; and in Loudon's 



