BOTANICAL GAZETTE. 



59 



unsettled condition of this group of plants it must be exceedingly 

 difficult for a philosophical mind to feel satisfied in their study, and 

 this is apparently exactly Prof. Tuckerman's position. The ordinary 

 multiplier of species would meet with no difficulty, but would reap 

 a rich harvest among the bewildering display of forms; but our 

 author has no such thought and with evident reluctance sends out 

 the present book with its species, " in great part, sufficiently well 

 settled. " All through the work one finds new things described,but 

 not as yet admitted to specific rank, and having only provisional 

 places. These, we are told, the author would have preferred to keep 

 back, "with Horace, nonum in annum." We are thankful however 

 that he did not in this case follow literally the precej>ts of the gen- 

 ial poet, for this work will enable more of us to help the author in 

 fixing the uncertain forms. There is usually no loss in putting out 

 a tentative work, for observers are never so provoked into reporting 

 their observations as when they think they are correcting blunders. 

 Our author also thinks that Lichenology has not kept pace with the 

 "diagnostic enumeration of new forms called arbitrarily species ; v 

 which same may be said of some other groups of plants. As stu- 

 dents of Phaenogamic Botany are in the habit of looking to Robert 

 Brown as the most philosophical observer, so the students of Lich- 

 ens look with equal veneration upon Elias Fries. 



In some 20 pages of introduction Prof. Tuckerman gives a cap- 

 ital view of the present status of our knowledge concerning lichens. 

 This is followed by a list of recent authors and a key to the 72 gen- 

 era, grouped under the two series,\(rymnocarpi, and Angiocarpi, 

 names that remind us of our series of Dicotyledons. Then follows 

 the body of the work, containing quite a full description of charact- 

 ers, localities, and relations of the species. Our copy happened 

 to be faulty, lacking pages 257-260 and thus depriving us of two or 

 three small genera; nor could we find Thamntilia in the index, al- 

 though it appears in the body of the work. 



Nearly 500 species are described, the largest genus being Le- 

 canora, numbering 56 species. The other large genera are Cladonia 

 with 35 species, Parmelia 30, Placodium 28, Collema 27, Leptogium 

 25, Pahnaria 24, Cetraria 22, and Physcia and Sticta each 21. This 

 shows remarkable uniformity in the size of the genera; but in the 

 other genera the number of species drops very rapidly into the sin- 

 gle digits. 



It is to be hoped and expected that one of the results of this 

 book will be the more earnest study of this puzzling group of plants, 

 which very fact will hasten the reading of many riddles. There is 

 no reason now why Lichens should not have as many devotees as 

 most other groups of Cryptogamia. — J. M. C. 



Action of Acids 011 Cellulose.— "Acids (especially sulphuric- 

 acid) when greatly diluted* cause starch grains and cellulose at the 



^Italics min o. L. S. 



