HAKDWICKE'S SCIENCE -GOS SIP. 



39 



graphical botany, might gather the impression that 

 all the species mentioned marked the Castle Eden, 

 or at any rate the East Durham district ; for it is 

 nowhere said, nor is any clue given, that such is 

 not the fact. Although not so stated, the various 

 plants named must have been found in three distinct 

 regions, the eastern and western as much as sixty 

 miles apart, and each differing widely from the 

 others in physieal characteristics and altitude, and 

 therefore also in their flora. The species peculiarly 

 abundant on the sandhills by the sea are rightly 

 stated; but the Crepis taraxaeifolia and Lepidium 

 latifolium (? was it not Braba, which forms a 

 striking feature of the spot) are introduced 

 species near Hartlepool, and were probably picked 

 off the weedy fiats of debris formed of ballast, lying 

 parallel to the sea, north of Hartlepool. Astragalus 

 hypoglottis grows plentifully upon the ballast, too, 

 but its indigenous habitats are the turfy magnesian- 

 limestone cliff-slopes near the sea, where also the 

 Orchis ustulata, the Privet and the Juniper, flourish 

 as natives. The Asplenium marinum, affecting 

 sheltered crevices of the sea-worn rocks, is scarce 

 now, growing only at Marsden and Blackball rocks, 

 and there diminutive in size and infertile, but 

 luckily, for the most part, out of reach of all but 

 good climbers. Woodsia ilvensis has never been 

 known save in one station — the Ealcon's Clints, — 

 a basaltic scar, almost on the Westmoreland border, 

 and is now probably quite extinct. One single 

 plant was seen and secured some five years ago by 

 a miner at Middleton-Teesdale, and this is the 

 latest occurrence I know of. Rubus chamcemorus 

 grows only on the sub-alpme moory plateaus of the 

 western peaks, common enough amongst the ling in 

 places, but never found at a lower elevation than 

 1,200 feet. The Ileum athamaniicum mentioned as 

 "seen in abundance" by Mr. Percival, was possibly 

 some other species : Ileum has never hitherto been 

 observed in the county ; so, if really correct, it is 

 an interesting discovery, and the locality (after 

 verification of the species by competent authority) 

 should be placed on record. Geranium pratense and 

 sylvaiicum occur together by riversides, and in 

 pastures in the hill dales, but the former descends 

 to lower levels, and adorns many waysides in the 

 central limestone districts of Durham. Gentiana 

 verna, Tqfieldia, and Potenlilla fruticosa are con- 

 fined to the higher parts of Teesdale, with Poly- 

 gonum viviparum (misprinted virginianum in the 

 paper) in the hilly pastures. Helleborus viridis, 

 the " dead flowers" of which it is said were seen, 

 is not an indigenous species in Durham — only a 

 naturalized one, and rare as that even, occurring 

 only in one spot by the Wear, and one or two by 

 the lower reaches of the Tees. 



Mr. Percival will, I trust, forgive these few 

 animadversions upon his remarks, made, as I make 

 them, solely with a view to remove possible mis- 



conception. My warrant must be that imperfect 

 statement leads to hazy ideas, and that even gossip 

 upon matters of science, if not definite in form 

 within the limit of its subject, is of little value to 

 anybody, if not entirely worthless. 



E. Arnold Lees, E.L.S. 

 Middleton Hull, Upper Teesdale. 



MICROSCOPY. 



A Simple Method of Removing Air-bubbles 

 erom Sections. — 1 have been closely engaged for 

 some time in the investigation of fresh mucous 

 tissue, especially in embryonic structures, and as I 

 invariably use the freezing process for cutting my 

 sections, I have beeu much troubled by the 

 presence of innumerable air-bubbles, which have 

 resisted all manipulation, and even the use of the 

 air-pump. The origin of the air-bubbles is, that in 

 freezing water expels some of its free air, and this, 

 involved in mucous tissue, presents such a fineness 

 of division as to defy mechanical treatment. I 

 looked, of course, for a solvent, and found it readily 

 in cold distilled water which had recently been 

 boiled. Boiling deprives water entirely of its air in 

 solution, but on cooling the water takes it up again 

 with great avidity. I place my section, as soon as 

 it is cut, on a slide, and then allow a very gentle 

 stream of the prepared water to flow over it for a 

 few minutes ; or, if the section will stand rougher 

 handling, I place it in a bath of the water. In this 

 way every trace of air-bubbles disappears. The 

 process is so simple that it may be applied to the 

 most delicate structures without injury. — Laioson 

 Tail, F.R.C.S., Birmingham. 



Atlas of theDiatomace.e, by Adolph Schmidt. 

 — We have had the opportunity of seeing the first 

 part of this work, which promises to be, when com- 

 plete, one of the most magnificent monographs ever 

 published. The author, who is well known in Ger- 

 many,has secured the assistance of the following gen- 

 tlemen: — Messrs. Grunow, Grundler, Weissflog, 

 Janisch, Pfitzer, and Eulenstein. The first part con- 

 tains 26 figures of various species of Actinoptychus 

 71 of Naviculce, and 21 of Surirellce. The plan adopted 

 by the author is to make an enlarged drawing of 

 the object (according to the prospectus, about 900 

 diameters), from which photographic negatives are 

 taken, and from them permanent copies are made 

 by the autotype or some analogous process (Licht- 

 driick). The price will be 6 marks (= 6 shillings) 

 to subscribers whose names are entered before a 

 stated period ; after that the price will be advanced 

 to 9 marks. A part will be published every two 

 months. The size of the plates is 11 by 9i inches 

 (German). The only work on the Diatomacese with 

 which it can be compared is "Ehrenberg's Micro- 

 geologie," but which is far inferior to it in the 



