Januaey 5, 1900.] 



SCIENCE. 



27- 



observers to be attained through water absorp- 

 tion or drying out, and purely hygroscopic 

 movements. Dissemination may occur by means 

 of air and water currents, and a quite well estab- 

 lished case is recorded in which Thysanura were 

 responsible for carrying the brood-bodies of Au- 

 locomnium and Androgynum. The projection 

 of the parts bearing brood-organs above the gen- 

 eral levels of the moss-turf is interpreted as an 

 adaptation for dissemination through such ani- 

 mal forms. Hook-like organs occur {Ephemerop- 

 sis and Bryum bulbilosum), which are subject to 

 similar teleological interpretation, though one 

 with difficulty escapes the conviction that the 

 point is somewhat far-fetched. Mucilaginous 

 outer membranes, which insure adhesion to 

 animal forms, are also present in some kinds. 



Of the remaining matters perhaps the most 

 important to mention here are the attempt to 

 determine whether correlation occurs between 

 the habit of producing gemmae and the con- 

 ditions under which the plants live, and to 

 estimate the taxonomic value of the organs in 

 question. 



The typography and numerous illustrations 

 are up to a high standard, but do no more 

 than justice to the thorough work of the author. 

 A full index of generic and specific names ex- 

 tends greatly the usefulness of the volume, 

 which will be of very great value to those bot- 

 anists who are interested in the biological 

 matters relating to the mosses, but whose 

 studies have not been directed to them in a 

 taxonomic way. It will also serve a good pur- 

 pose in enabling the student who may be 

 contemplating research in these lines to orien- 

 tate himself historically. This will be facili- 

 tated also by a very complete bibliography. 

 Francis E. Llotd. 



From a systematic standpoint this work is of 

 great value to American students, for of the 110 

 species described, 52 are known to occur in this 

 country, and 108 out of the 187 figures refer to 

 them. Systematic books have overlooked asex- 

 ual methods of reproduction except in such 

 cases as Georgia pellueida, Aulacomnion palustre, 

 Tortula papillosa, and a few others where the 

 means were so conspicuous as to defy ignorance; 

 hence it will be a surprise to learn that Dicra- 



num sooparium, Funaria hygrometrica, Bryum 

 argenteum and Dicranella heteromalla, though 

 commonly found fruiting, have also methods of 

 propagation. Those species which are conspicu- 

 ous for their brittle leaves are many of them 

 rare in fruit, forming new plants from the frag- 

 ments of the leaves, but an interesting addition 

 to the list having this method is Anomodon tris- 

 tis, which thus far is unknown in fruit. The 

 ' Confer vae Orthotrichse,' those brown septate 

 bodies which occur on the leaves of various spe- 

 cies of Orthotrichum and Grimmia, have long been 

 familiar, but few students have realized why so 

 many species of Campylopus, Tortula, Bryum and 

 Plagiothecium were more often found sterile than 

 fertile, nor how they reproduced in spite of this 

 fact. Climates where sexual reproduction is 

 diflBcult cause a greater development of other 

 methods, and dioicous species are more apt to 

 develop asexual methods than monoicous ones. 

 An artificial key is given by which the asexually 

 propagative species may be classified according 

 to the modifications of the stem, leaves and pro- 

 tonema ; it will be useful in encouraging the 

 study and collection of such species as have 

 been ignored or overlooked on account of lack 

 of fruit. The work has paralleled that of F. 

 De Forest Heald, published in the Botanical 

 Gazette for 1898, but it is more extensive, and 

 the author claims to have found that Bryum an- 

 notinum, Pleuridium nitidum hulbillifera and Lep- 

 tohryum pyriforme are identical. There is a 

 similar identity between Pottia riparia Austin, 

 which antedates Leptodontium Canadense Kindb. 

 and Trichostomum Warnatorfii Limpr. , all of 

 which propagate by clusters of septate propa- 

 gulae borne on the paraphyses, seemingly re- 

 placing the archegonia, hence all but Pottia 

 riparia have thus far been only found sterile- 

 Under whatever genus the species is recognized, 

 that of Austin has priority, a fact to which I 

 have already called attention. 



E. G. Bbitton. 

 N. Y. Botanical Gardens, 

 Bronx Park. 



The Physical Nature of the Child and how to 

 Study it. By Stuart H. Eowe, Ph.D., 

 Supervising Principal of the Lovell District, 

 New Haven, Conn. ; formerly Professor of 



