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 inch and half-inch, still more so. Those lenses, fitted in horn cases, may be obtained from any of our local opticians at from 1s. upward, the price varying according to the finish of the article. If the School Microscope mentioned below is obtained, one or more of the lenses supplied with it may be made to do service in the field; but, if so used, should always be carried in a small chamois leather bag to protect from scratches.

It is advisable to acquire the habit of constantly using a lens, making out by its aid all the details possible, such as the position of the leaves on the stem, general characters, &c., noticing whether they are straight, curved, falcate, and so on, and their direction when dry. This latter character is often a ready guide to nearly allied species. For instance, two mosses common on wall tops, Bryum capillare and B. caspiticium, differ materially in appearance when dry, the former having the leaves remarkably twisted, the latter having them straight and imbricated. Many other like cases might be cited.

A good text book will, of course, be indispensable. There are several to select from, published at various prices. For instance, Stark's "British Mosses," having twenty coloured plates, is offered for 5s.; but this is not to my thinking a satisfactory book, the descriptions being too vague to be useful; still, many of the more frequent mosses may be made out from it. Berkeley's "Handbook of British Mosses," with twenty-four coloured plates, costs 21s. new, but may frequently be obtained second-hand for about 11s. The great fault of this work is that the nomenclature is not in all cases that most generally adopted, and the author gives no synonyms. This, I think, is a serious fault, as it leaves one in uncertainty as to the name adopted by other authors. Of cheap books the one I prefer is C. P. Hobkirk's "Synopsis of the British Mosses," which costs 7s. 6d. The only fault is the absence of plates. It is so handy in size that it may be carried in the pocket without inconvenience, contains excellent descriptions of all our British mosses, and the classification adopted in it is excellent. But the best text book is Wilson’s "Bryologia Britannica." It contains excellent illustrations of all the mosses described in the volume, giving figures of many of the minute details. The descriptions are admirable, being these of one of the best bryologists our country has produced. Any student who makes good use of this work will find that most of the difficulties surrounding this study will be rapidly overcome. This is somewhat expensive book, costing 42s. with the plates uncoloured, or 84s. with the plates coloured. The uncoloured edition is to my thinking quite as useful as the more expensive one. I should certainly advise the student to got this volume as his text book.

Of course a microscope will be almost, if not quite, indispensable. These instruments, as everyone knows, are very varied in price, a first-class microscope being an expensive luxury, though there are in the market excellent instruments at most moderate prices. But a great amount of good work may be done with a cheap microscope—in fact, a great deal of the best work that has been done for science has been done with comparatively inexpensive instruments.