270 



SCIENCE-GOSSIP. 



contracts and disappears in drying, so that there 

 is no need to use it too sparingly in mounting. For 

 mounting foraminifera in balsam, a little of the 

 same gum may be diluted with distilled water, 

 until it forms a perfectly clear liquid. A drop of 

 this on the glass slip will be sufficiently strong to 

 hold the foraminifera in position ; and at the same 

 time will not show, provided the mount is 

 thoroughly dried before the balsam is added. 



A Curious Swimming Fern. — At a recent 

 meeting of the Leeuwenhoek Microscopical Club, 

 Manchester, Mr. C. Bailey described the life- 

 history and structure of a curious swimming fern, 

 Salvinia natans, Willd. This plant is allied to the 

 pillwort, Pihuaria globuli/era, Linn., and it is 

 distinguishable from the true ferns by its possessing 

 two different kinds of spores, one kind being very 

 much larger than the other. It occurs in 

 abundance on the Continent, especially on the 

 neighbouring coasts of Belgium and France, but it 

 has not yet been found anywhere in the British 

 Isles. Theplant 

 passes the 

 whole of its life 

 in fresh water. 

 Initsadultstate 

 it floats on the 

 surface with its 

 green fronds or 

 leaves. De- 

 pending from 

 the undersides 

 of its stem are 

 long submerged 

 leaves which 

 take upon them- 

 selves the form 

 and functions of 

 roots (fig. 1). 

 Its spores are 

 contained in 

 little globular 

 capsules, or 

 spheres, termed 

 sporocarps, 

 found at the 

 base of the 

 fronds and close 

 to the stem. 

 These sporo- 

 carps help to 

 sustain the 



floating plant by means of the air canals 

 which run within the external ridges of the 

 capsule (figs. 2 and 3). The spores are dis- 

 seminated first by the sporocarps breaking off 

 from their stalks at their points of junction with 

 the leaves. These in their turn float by means of a 

 coating formed of hardened mucilage mixed with 

 minute bubbles of air. In the early spring 

 germination ensues, thus completing the life-cycle. 

 The main features of the minute anatomy of the 

 organs are shown in the following figures. Fig. 4 

 represents a section across a group of three 

 sporocarps, one with macrosporangia (ma) and 

 two with microsporangia (mi). Fig. 5 shows a ripe 

 microsporangia, x 300, with the tubes of the 

 microspores (t) breaking through. 



The Quekett Microscopical Club. — The last 

 journal of proceedings of this society contains 

 ".Infection of Ducks," by J. B. Rosseter ; "Fora- 

 minifera," by A. Earland ; a note on the " Male of 

 Proales wernechi," by C. F. Rousselet ; " Logarithmic 



Swimming Fern 



Plotting of Data," by D. C. Scourfield ; an account 

 of " Peripatus moseleyi," by the Rev. J. R. Ward ;. 

 and numerous interesting notes on " Diatom 

 Structure," " Mycetozoa " and "Double Colour 

 Illumination." Mr. A. Earland's very practical 

 paper, on " The Best Methods of Collecting and 

 Preparing Foraminiferous Materials," is full of hints 

 and suggestions, and it will well repay perusal. 

 In " A Short Note on Minute Diatom Structure," 

 Mr. E. M. Nelson reports two further results in 

 the resolution of fine diatomic structures. The 

 first is the detection of the long-shaped aperture 

 in the nodule of Navicula rhomboides; the second 

 relates to a diatom Biddulphia elaborata mounted in 

 styrax, in which a delicately perforated membrane, 

 not hitherto discovered, has now been made out 

 with the assistance of the new Powell apochro- 

 matic adjustable condenser. Oblique illumination 

 completely obliterates this structure, which can 

 only be seen by means of a direct axial cone of maxi- 

 mum dry aperture. We note also that at a recent 



meeting of this 

 club Mr. G. 

 Massee gave 

 an address, "On 

 the Evolution 

 of the Basidio- 

 mycetes," illus- 

 trated by a 

 series of col- 

 oured drawings 

 and blackboard 

 sketches. He 

 described the 

 fructification of 

 this class of 

 fungi and the 

 various means 

 taken by the 

 different fam- 

 ilies for distri- 

 buting the basi- 

 diospores. At 

 the same meet- 

 ing Mr. Good- 

 win briefly 

 described his 

 method of in- 

 creasing the size 

 of the image of 

 the lamp flame 

 by placing a 

 weak convex lens under the lower combination of 

 the condenser. 



The Micro-Structure of Alloys. — At a recent 

 Conversazione of the Royal Society, a series of 

 photographs were shown demonstrating that when 

 fluid mixtures of metals and non-metals are allowed 

 to cool, crystals of definite chemical composition 

 are formed. They may be clearly seen with the 

 aid of a microscope after the polished surfaces 

 have been etched with dilute acids, or tinted with 

 suitable re-agents. 



The Fig Scale. — In the land areas in and 

 around the Mediterranean, scale insects are num- 

 bered among the most destructive pests that the 

 orange and fig growers have to contend with. Of 

 these Coccus nisei, the parasite of the fig, is just now 

 attracting much attention in Italy. The diameter 

 of a well-developed female is five millimetres, the 

 colour is greyish-white, and they have the appear- 

 ance of small cones upon the trunk and boughs of 



'va 



