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IfARD WICKE'S SCIENCE-GOSSIP. 



BOTANY. 



Ozone given off by Plants. — Investigations 

 which may have a decidedly practical tendency have 

 been made by Drs. J. M. Anders and G. B. M. Miller 

 on the production of ozone by plants. Their experi- 

 ments, which were made by way of testing results 

 which had been obtained before, lead them to the 

 following conclusions. First, that both odorous and 

 inodorous flowering plants generate ozone, but the 

 former the much more actively that, so far as tested, 

 scented foliage, especially pine and hemlock, produces 

 it ; and finally that a necessary condition apparently 

 is the presence of the sun's rays, or at least a good 

 diffused light. It is evident that the power thus 

 shown to be possessed by plants is an important factor 

 in deciding the question of their cultivation indoors, 

 though it does not follow that the net results are 

 beneficial. As to the pine, the authors conclude 

 their paper (which may be found in the " American 

 Naturalist " for September), by saying that " since the 

 exhalations from the pine foliage are active agents in 

 generating ozone, it follows that all of the important 

 hygienic advantages of ozone are to be derived, to a 

 marked degree, from the presence of pine woods." 



The Botanical Exchange Club. — Two Reports 

 of this Club are to hand, those for 1883 and 1SS4. 

 The latter shows an increase by some hundreds, in 

 the number of plants received for distribution, over 

 the previous year. The greater part of the Reports 

 consists of notices of plants, naturally with somewhat 

 unfamiliar names, with observations appended, pre- 

 sumably those of authorities to whom the plants were 

 forwarded for identification. 



How Plants Grow.— The first paper in the 

 "Journal of Microscopy " for October is one with the 

 above title, by Mr. H. W. S. Worsley-Benison, F.L.S. 

 The paper may be taken as a sequel or continuation 

 of the one on "What is a Plant?" and in it the 

 author touches in succession upon the vegetable cell 

 as an individual, the cell in combination, cell forma- 

 tion and growth, and the reproductive processes — 

 fertilisation, embryonic growth, and germination — 

 to show the origin of the primary cell. The methods 

 of feeding, moving, climbing, and reproducing are, 

 he says, worthy of a separate paper, and are, for the 

 most part, passed over here. 



"The British Moss Flora."— The ninth part 

 of Dr. Braithwaite*s important work on " British 

 Mosses " is now out, and bears date of September. 

 It contains the second part of Fam. VIII., Tortulacere, 

 and consists of the usual letterpress and four plates 

 full of figures. This work is published by the author, 

 at 303, Clapham Road, London. 



The Common Sunflower.— The flowers are 

 proterandrous, although the stigmas emerge at the 

 same time that the pollen is shed, but the stigma- 



lobes do not separate and curl back until after the 

 pollen has been distributed or lost its virtue. Briefly, 

 the process seems to be thus : The stigma, with its 

 lobes closely appressed, is thrust through the tube 

 formed by the synandrous stamens. The stigma- 

 lobes are papillose on their outer surface, and the 

 dehiscence of the anthers is introrse. Consequently 

 the pollen is forced upward by the ascending stigma, 

 aided by the papilla? on the latter, and, as the anthers 

 are then very prominent, insects readily come in 

 contact with the pollen. Afterwards the stigmas 

 become more projected, separate, and, in curling back, 

 force down the anther tube into the corolla. I do 

 not think either shrinkage or bees have anything to 

 do with the depression of the stamens. The object 

 of forcing back the stamens seems to be that of getting 

 the stigmas in the same relative level as the anthers 

 had been. Mr. Swan said nothing about the copious 

 secretion of viscid saccharine matter on the unopened 

 buds in the centre of the head. Upon this the bees 

 sometimes alight, and may be seen busily feeding. 

 They then resort to the flowers, working from the 

 centre to the circumference, and in doing so convey 

 pollen from the inner florets to the projected stigmas 

 of the outer ones, but I fail to perceive in this any 

 special arrangement to secure cross-fertilisation 

 between different capitula. If the insect worked 

 from circumference to centre (and, seeing that the 

 ray-flowers are the most attractive, one would think 

 that this were the case), the adaptation to secure 

 cross-fertilisation would indeed be perfect ; but I have 

 been informed, on good authority, that the bee 

 generally works from centre to circumference, which 

 process would simply secure cross-fertilisation between 

 the inner and outer whorls of florets on the same 

 head. My own observations upon numerous plants 

 in my garden do not satisfy me that bees have a 

 preference for one mode above the other, but that 

 they alight without much discrimination, and 

 commence operations at the nearest accessible point. 

 Mr. Swan's theory, that stamens and pistil are 

 developed spines, does not appear probable. Con- 

 sidering the normal number of the parts, their 

 consistency with the arrangement in other compositse, 

 and the evidence afforded generally by analogy, it is 

 unlikely that in sunflowers the stamens and pistil are 

 developed spines, unless Mr. Swan means to say 

 that in the composite generally, the parts are thus 

 developed. If, however, they are, to what organs do 

 these spines belong ? In the sunflower, their object 

 is evidently to prevent the depredation of insects. 

 The immunity of sunflower leaves from insect attacks 

 has often been noticed, and Kerner supposes that 

 they contain juices or secretions distasteful to the 

 insects. In my opinion, the stiff bristles on the stem, 

 branches, and leaves are quite sufficient to account 

 for their freedom from insects. In my garden, plants 

 with glabrous leaves were literally beset this summer 

 with aphides, but not one could be seen upon the 



