280 



HARDWICKE'S SCIENCE-GOSSIP. 



ZOOLOGY. 



Acme lineata. — In vol. xix. of Science-Gossip, 

 p. 185, reference is made to the distribution of Acme 

 lineata, var. alba (Jeffr.), which does not appear to 

 have been found in this country. It may therefore 

 be of some interest to your readers, to hear that 

 I have found this shell near this city, in the same 

 locality as the type, which, however, has only been 

 found by me occasionally, and then only very 

 sparingly. In the list of "South Devonshire 

 Mollusca " of the Exeter district, given at p. 115 of 

 vol. xxv., no mention is made of this shell. — 

 /. W.D.K., Exeter. 



The Preservation of Sea-Urchins. — I have 

 found that by cleaning out the internal portions, then 

 thoroughly washing in fresh water and drying, the 

 spines do not come off. — D. Wilson Barker. 



BOTANY. 



Vegetable Symbiosis — At the Annual Soiree of 

 Manchester Microscopical Society, Prof. Weiss gave 

 an address on this interesting subject. He pointed 

 out that partnerships for mutual benefit or for 

 defensive purposes are often formed in the animal 

 kingdom, and are also of no uncommon occurrence 

 between plants and animals. Thus the whole group 

 of myrmecophilous, or ant-lo\ing plants, harbour in 

 the hollows of their stems entire armies of ants, 

 which they feed with nectar secreted on their leaves. 

 The benefit to the ant is apparent, and that reaped 

 by the plant is the protection afforded by an army of 

 these honey -eating ants against the disastrous ravages 

 of the leaf-eating ants. These assail almost all trees 

 of the tropics, but are always driven back by the 

 garrison maintained by myrmecophilous plants. 

 Another instance is the occurrence of small green 

 algae within the tissues of certain animals, such as 

 the freshwater sponge and the freshwater polype 

 (hydra). These green-coloured bodies were long 

 held to be green corpuscles belonging to the animal 

 itself, but have now been shown to be vegetable cells 

 which have been able to be cultivated outside the 

 animal body. As these green cells can form starch 

 and ultimately sugar, which transfuses out of the algae 

 into the body of the animal, it is evident that they 

 are of great benefit to the animal, while the algae 

 themselves can absorb certain substances out of the 

 animal cells. An analogous example occurs in the 

 vegetable kingdom in the case of the lichens, in 

 which some green alga is associated with a fungus. 

 Every lichen consists of the two different organisms, 

 and the green cells form, under the influence of the 

 light, food-substances which are made use of by the 

 fungus. In initial stages the fungus can be seen 

 capturing, with its threads, the algae cells of which it 



makes use, and which are the working partners of the 

 concern. In another case we have an association of 

 a fungus with a beech or oak or other tree. The 

 roots of these are often found infested with fungal 

 threads or hyphae, termed mycortiza, which are able 

 to take up the decaying vegetable matter and pass it 

 on to the tree. Seedlings of the oak or beech are 

 unable to grow in decaying leaf-mould, without the 

 aid of such fungi. Here, then, the green plant is the 

 one which derives the greatest benefit, and not the 

 fungus, as was the case in the lichens. Many bog 

 plants, such as the heath and the crowberry, have 

 formed similar partnerships with fungi, the fungal 

 threads making their way into the roots of the plants 

 and living for a time in their cells. Ultimately, 

 however, they are entirely absorbed by the green 

 plant, and the advantage of the partnership to the 

 fungus is not apparent. In the root tubercles, so 

 characteristic of leguminous plants, we find small 

 bacteroids, which have made their way in and which 

 in 'exchange for some food-matter, which they absorb 

 from the pea or bean, provide it with the necessary 

 nitrates which they can form from the nitrogen of the 

 air. Thus leguminous plants, and those only, which 

 are infected by the bacteroids, can grow in a soil 

 entirely devoid of nitrogen, where no other green 

 plant could possibly exist. Leguminous crops are 

 invaluable to farmers, as they leave the ground 

 stocked with nitrates, when the root tubercles 

 decay. Lastly, a case of symbiosis has recently been 

 discovered by Professor Marshall Ward in the 

 fermentation of ginger beer. Of the many organisms 

 contained in the so-called "ginger beer plant," two 

 only are necessary for normal fermentation — a yeast- 

 like fungus, and a bacterium ant ; these are so 

 dependent one on the other that the fermentation 

 they produce may well be called symbiatic fermenta- 

 tion. The yeast cell produces a waste product, 

 which, when accumulated, stops all further action. 

 The bacterium, however, feeds on this waste product, 

 and thus, by removing it, stimulates the yeast-like 

 fungus to renewed activity. Thus both partners in 

 the concern are benefited, and dependent one upon 

 the other. 



The Mudah and Toothache. — I was told by 

 the natives of India, that the milky juice of the 

 mudar {Calotropis gigantea), dropped into an aching 

 tooth, instantly relieved the pain, but so loosened 

 the tooth in its socket, that it generally dropped out 

 soon after. This seemed to me so very improbable, 

 that I gave the matter no further thought until 

 a European friend told me he had tried it. He said 

 that there was first a moment of intense agony, then 

 total cessation of pain, and that the tooth actually did 

 drop out a short while after. Accordingly, the next 

 time I had a toothache I tried it myself, with absolutely 

 no effect. The pain was neither relieved, nor 

 aggravated ; and the tooth was not perceptibly 



