April II, 1872] 



NATURE 



459 



live, not only from the richness of the flora, but frorh the 



large number of endemic monotypes (monotypic genera 

 or sub-genera, or widely distinct species), confined to very 

 restricted areas, and of disjointed species — identical species 

 in widely dissevered areas. With regard to the species of 

 narrowly confined stations, Prof. Grisebach believes that 

 the considerations he has brought forward tell decidedly 

 in favour of the conclusion " that monotypes and other 

 rare organisms are not— or, at least, are not generally— 

 to be regarded as the surviving remains of earlier crea- 

 tions, but as evidences of the productive power of the 

 locahties where they are now to be found, and from 

 whence no means of migration are within their reach " 

 (p. 364). He can, however, scarcely have paid attention 

 to the various proofs recorded of the gradual reduction 

 of the areas of several Mediterranean species, even within 

 historical times, and still more since an immediately 

 preceding geological epoch — that of the formation of the 

 tufas of the south of France. He does not, indeed, seem 

 to be aware of the instructive memoirs on this subject of 

 Gustave Planchon (see Nat. Hist. Review, 1865, p. 202). 



The "disjointed" species, on the other hand, appear to 

 have puzzled Prof Grisebach, as they have done and will 

 continue to puzzle all speculators on Geographical Botany. 

 Grisebach endeavours to reduce their number as much as 

 possible ; sometimes by the discovery of intermediate 

 stations ; then, again, by presumed colonisation through 

 man or other agencies ; or by showing that supposed 

 identical forms in distant areas are really distinct species, 

 and, therefore, beyond the scope of inquiries limited to the 

 age of now-existing species. But yet, in the Mediterra- 

 nean as in the Japanese provinces, he is obliged to admit 

 some which occupy two limited areas separated by 

 enormous intervals. Thus, although he supposes that the 

 appearance of Rhododendron po)tticunt on the coast of 

 Portugal may have been the result of introduction by the 

 Arabs, that Gcnm heierocarpum, now only known from 

 the mountain regions of S. Spain and of Elborus in 

 Persia, may yet be found in intermediate localities ; yet 

 such suppositions, he admits, can in no way account for 

 the disseverence of the Cedar in the Atlas, the Lebanon, 

 and the Himalaya, or of the Piniis excelsa in the moun- 

 tains of Macedonia and the Himalayas. Unwilling to 

 admit that these and other instances (far more numerous 

 than acknowledged by Grisebach) of widely dissevered 

 stations may be the remains of once continuous areas 

 he suggests the possibility of the transference of seeds by 

 winds, birds, &c. Birds are, indeed, probably powerful 

 assistants in the migrations of plants. But the effect 

 of winds has been much overrated, as shown for 

 instance by Kerner in a paper recently published in 

 the Zeitschrift dcs Dcutsclicn Alpenvcnins, and is 

 made more of perhaps by Grisebach in the present 

 work than by any other observer, and not always on the 

 safest data. Thus he attaches (p. 3S9) great importance 

 to an " unpubhshed memorandum of Berthelot's,'' that is 

 to a label to a specimen of Erigeroii ainbiguus, bearing 

 the words " cette composde, qui a quelques rapports avec 

 les Conyza, est devenue tres-commune sur toutes les 

 cotes de Tendriffe apres le dernier ouragan." Tliis memo- 

 randum is amplified into " On the Canary Islands whose 

 flora w-as so well known to him, this traveller saw, imme- 

 diately after a violent hurricane, an annual Synantherea 



{Erigeron ambi^ms) which is generally dispersed over 



the Mediterranean flora, suddenly germinate and take 

 permanent possession of the soil in the most diversified 

 stations," the amplification thus including some half-a- 

 dozen statements not contained in the original memo- 

 randum, adding especially the propter hoc to the post 

 hoc. Erigeroii ambiguus is one of those plants of which 

 a single individual will produce seed enough to cover a 

 considerable tract of country in the next following season, 

 if favoured by a suspension of those counteracting influ- 

 ences which annually destroy all but one out of thousands, 

 either in the state of seed or of the infant plant ; and in 

 Berthelot's memorandum we find no evidence either that 

 the plant was not in the islands before the storm, or that 

 the seed was actually brought by the storm, or that if so 

 brought its germination and early growth were so excep- 

 tionally rapid, as to show the plant in an observable stage 

 " immediately " after the storm. The inquiry, however, 

 into the causes of the disseverance of areas, whether due 

 to the gradual extinction of old races, or to the colonisa- 

 tion of new ones, remains one of the most interesting 

 problems for solution in Geographical Botany. 



OUR BOOK SHELF 



Consumption, and the Breath Rebreathcd. By Henry 



MacCormac, M.D. (London: Longmans, 1872.) 

 This work is written con amore by an enthusiastic 

 physician, who has satisfied himself of the truth of the 

 theory he advances, and is now desirous of convincing 

 the rest of the world. The theory broached by Dr. Mac- 

 Cormac is that phthisis or pulmonary consumption, as 

 well as tubercle generally, is always and exclusively the 

 result of the breathing of air that lias already been vitiated 

 by respiration. It is well known that air that has once 

 passed through the lungs has undergone important 

 changes. Its oxygen is reduced in quantity, a nearly 

 corresponding amount of carbonic acid has been added, 

 and it also contains certain organic compounds the nature 

 of which has not been very satisfactorily determined, but 

 which are undoubtedly of an eftete nature, and analogous 

 in their composition to the disintegrated organic com- 

 pounds eliminated from the body by the other excretory 

 organs. The extremely deleterious action of the re- 

 introduction into the system of the materials discharged 

 by the intestines is now very generally known, from 

 the inquiries that have been instituted into the nature and 

 origin of typhoid fever; and Dr. MacCormac is perfectly 

 justified from analogy in attributing serious results to the 

 re-introduction into the system by the lungs of the air 

 which has once passed through it, and which is con- 

 sequently charged with decomposing substances. The 

 carbonic acid alone is bad enough, but even if this were 

 removed as fast as formed and replaced by oxygen, while 

 the animal still continues to breathe the air it has already 

 expired, there can be little doubt that it would speedily 

 feel the effects of the other impurities with which expired 

 air is charged. Under ordinary circumstances the only 

 means of avoiding these effects is to permit free access of 

 air to all and every apartment in which man is confined 

 either by day or night ; and so far we cordially endorse 

 the views and recommendations of the author of the work 

 before us. But when Dr. MacCormac states that tubercle 

 is exclusively the result of breathing expired air, we think 

 he carries his theory too far. We cannot put aside in the 

 facile manner he adopts the influence of hereditary pre- 

 disposition, nor the effects of exposure to damp and 

 cold, when combined with insufficient food. Imperfect 

 ventilation is so common that it is almost always as- 



