G8 



KNOWLEDGE 



[Makch, 1903. 



genus Cratxgiis, oar onlj species, the Hawthorn, needs no 

 description. In this genus the seeds are enclosed in a 

 bony case, instead of in cartilaginous cells as in Pyrus. 

 The remarkable thorns which render the plant so for- 

 midable are the attenuated terminarious of the branches. 

 They resemble in this respect the prickles of the Gorse, 

 and have a quite different origin from the [)riekles of the 

 Bramble or Rose. The function of the Hawthorn spines 

 is undoubtedly protective. The last genus of Fomaceas, 

 Cotoneaster, has, like Crahetjus, but a single British species, 

 and this is confined to a single locality —C. vulgaris, which 

 grows, though now nearly extinct owing to the incursions 

 of thoughtless collectors, on Great Orme's Head. It is a 

 small shrub, with ovate leaves, pink flowers, and red 

 berry-like fruit. 



Conducted hij M. I. Cross. 



NOTES ON THE COLLECTION, EXAMINATION AND 

 MOUNTING OF MOSSES AND LIVERWORTS. 



By T. H. Russell. 

 (Continued from page ^h.) 

 Before dealing in detail with the subject of mounting, let 

 me add a few words with reference to registering slides and 

 specimens, &c. My plan has been to have one general register 

 of slides, in which the various mounts are entered consecutively 

 as completed. Each page is ruled in five columns, headed 

 respectively, "Number," "Date when gathered," "Name," 

 "Habitat, &c.," and "Remarks.'' The label on the slide, in 

 addition to briefly recording the name, locality, and date, bears 

 the number corresponding with the entry in the Register, and 

 this number is also marked on the packet containing some 

 spare material for future use, if required. I also have a copy 

 of the " London Catalogue of British Mosses and Hepatic® '' (a 

 work, by the way, of which we are badly in want of a new 

 edition, that of 1881 having been long since exhausted), which 

 has been inter-leaved, the numbers in the " Catalogue" cor- 

 responding with the names of the various plants being repeated 

 on the added pages. Opposite to each of these numbers I write 

 the numbers of the slides in my collection referring to the 

 particular ])lant in question. Thus, Bnjiim alpinum is numbered 

 337 in the " Catalogue," and against this number I find entered 

 "105, 71'J," which gives me the references to the two slides of 

 this species in my collection. By the help of these two registers 

 I can always find the slides I possess of any particular moss, 

 and also the details of place and time where and when it was 

 found. I have another register, which is divided into columus 

 (two to a page), each of which is numbered and named in 

 correspondence with the " London Catalogue," and there I can 

 enter a short note of any moss I may meet with but which I 

 do not wish to mount. Lastly, I have a small book in which I 

 record the medium used for mounting and sealing each slide, 

 with the date of each of these operations. I have found the 

 above registers extremely useful, and if entered up systematically 

 they really give very little trouble. 



II. — MonNTIXG. 

 Owing to their small size and the facility with which their 

 original freshness can be revived, as already noticed, mosses 

 can be far more satisfactorily preserved than is possible with 

 ordinary flowering plants. The greater number may be readUy 

 mounted on the ordinary glass slips, and in this form they not 

 only occupy a comparatively small storage space, but remain, 

 for all practical purposes, as fresh as when they were gathered. 



I have specimens in my collection now that were put up 

 twenty years aad more ago, and which have altered little in 

 appearance in the meantime. 



I have tried several materials and compounds for mounting 

 purposes, but unhesitatingly give the palm to glycerine jelly, 

 both on account of the facility with which it may he manipu- 

 lated, and by reason of its admirable preservative powers. I 

 have for many years made my own jell}' according to the 

 following receipt, which is a slight variation on that given in 

 Carpenter's work on "The Microscope.'' Take 2 ounces (by weight) 

 of "invalid" gelatine, 6 ounces of water and tj of glycerine. 

 Soak the gelatine in the water until it swells (this takes about 

 40 minutes), then place the vessel containing tha gelatine and 

 water (a jam-pot is very serviceable ; it should be provided 

 with a cover of some kind) in a saucepan of water, and boil over 

 a slow fire until the gelatine melts. When the gelatine is cool, 

 but still liquid, add the white of one egg, and mix well. Boil 

 the gelatine, as before, until it becomes thick with the coagulated 

 albumen — this takes about half an hour ; add the glycerine 

 and 25 or 30 drops of carbolic acid and mix well ; strain through 

 filter-paper before the fire, and a clear pale yellow jelly should 

 be the result. 



I propose to describe my ordinary process of mounting with 

 this medium. The specimen to be mounted must first be 

 cleansed from all earth and grit in water, and the sjjores and air 

 gently expelled from any capsules by means of the dissecting 

 needles ; it must then be left to soak for at least 24 hours in a 

 mixture composed of water li ounces, rectified spirit lA ounces, 

 and glycerine ."i drachms : the small china pans in which moist 

 water colours are sold are very useful for this purpo.se. When 

 the specimen is taken from this preparatory liquid in readiness 

 for mounting care must be taken to remove the fluid adhering 

 to it as far as possible ; this may be done by placing it on a 

 glass slip, and tilting this so as to allow the superfluous hquid 

 to drain off, and then, last thing, applying blotting-paper. 



A hot-water bath is essential for mounting with glycerine 

 jelly ; mine consists of a small glass tumbler, provided with a 

 closely-fitting tin cap or Ud. A piece is cut out of this lid at 

 the margin, leaving a space just wide and large enough to admit 

 the neck of a small glass bottle containing the jelly ; this bottle 

 can thus hang in the hot water in the tumbler, when the lid is in 

 place, by mean? of its lip, which rests on the top of the tin 

 cover, and in this way the jelly is kept melted, and is, moreover, 

 close at hand for use. When my mounting is likely to take 

 long I wrap a piece of flannel round the tumbler in order to 

 retain the heat in the water as long as possible. The glass slip 

 on which the mount is to be made, as also the cover-glass, must 

 be first carefully cleaned in water : acetic acid is useful for 

 removing all traces of grease, and nothing serves better for 

 drying the glasses than an old, soft cambric handkerchief. The 

 glass slip is placed upon the flat tin cover of the hot-water 

 bath, and the specimen, after being freed from the preparatory 

 fluid, is laid on it. A few drops of the liquid jelly are then 

 taken from the bottle by means of a small glass pipette, and 

 are dropped on to the specimen. While the jellj' is kept liquid 

 by the heat of the water-bath all air-bubbles must be carefully 

 removed with the dissecting needle, and here the binocular 

 dissecting microscope will be found most helpful. Too much 

 care cannot be taken in this somewhat tedious process, as the 

 success of the slide practically depends upon the thoroughness 

 with which it is carried out. 



Nothing detracts more from the appearance of a mount when 

 viewed under the microscope than the presence of these dis- 

 figuring silvery globes, lurking among the delicate leaves, or 

 perhaps entangled in the teeth of the peristome, and my own 

 rule always is that, rather than allow a serious blemish of this 

 kind, the slide must be sacrificed, or the mount be recommenced. 

 I have found it a great help in many cases, especially when an 

 object likely to retain air, or an undue amount of the pre- 

 paratory fluid is in hand — as, for instance, a large empty 

 capsule, or a plant with the leaves closely covering the stem — 

 to put it into a little jelly on a spare glass slip, and theu to 

 extract the air as far as possible before transferring it to the 

 slip on which it is to be mounted. The whole plant thus 

 becomes more or less saturated with the melted jelly, and the 

 air-bubbles cannot find their way 'Oack to the mount, as they are 

 apt to do if the whole process is carried out on the one slide. 

 A second hot-water bath is not uuf requently of much assistance. 



