July 7, 1905.] 



SCIENCE. 



21 



It is interesting to note, as pointed out by 

 Mr. Lyon, tliati this unusually large number 

 of young is coincident with the possession of 

 four manimse, whereas two is the number 

 known in other bats. 



That the mammae of an animal should be 

 as many as the normal number of young pro- 

 duced would appear to be a reasonable propo- 

 sition, but that the normal number of young 

 equals the number of mammae is quite a dif- 

 ferent one, from which many exceptions will 

 suggest themselves. For instance, the seals 

 have four mammae, yet one young is the rule 

 and two the exception among the species with 

 which I am familiar. 



The fact of an increased number of mammae 

 in these bats correlates well with the observed 

 fact of an unusual number of young, and I 

 would be pleased to know of farther observa- 

 tions that may tend to establish what is the 

 average number. Henry L. Ward. 



Public Museum, Milwaukee. 



BOTANICAL NOTES. 



PLANT CELL STUDIES. 



Under the title of ' Stu.dies on the Plant 

 Cell ' Dr. B. M. Davis is bringing together in 

 a series of articles published in the American 

 Naturalist (May, 1904, to April, 1905) what 

 is known of the structure and activities of 

 the plant cell. This is necessary because of 

 the inadequacy and incompleteness of the ac- 

 counts to be found in even the most recent 

 botanical text-books. The author hopes, also, 

 to ' help to change an attitude toward investi- 

 gations on the plant cell that is unfortunately 

 too prevalent among botanists,' i. e., to regard 

 cytology as a very special field with an elab- 

 orate technique beyond the capabilities of the 

 average botanist. In carrying out this plan 

 the author divides the subject into six sections, 

 viz.: (I.) The structure of the plant cell; (II.) 

 the activities of the plant cell; (III.) highly 

 specialized plant cells and their pecviliarities ; 

 (IV.) cell unions and nuclear fusions in 

 plants; (V.) cell activities at critical periods 

 of ontogeny in plants; (VI.) comparative mor- 

 phology and physiology of the plant cell. The 

 treatment under each of these heads, as far as 

 published, is very satisfactory, and the author 



has certainly succeeded in making a most lucid 

 statement in regard to every point. Where 

 necessary he does not hesitate to indicate our 

 lack of knowledge in regard to any structure, 

 as when he discusses the nucleolus, and says 

 that its substance is not well understood. Yet 

 he does not refrain from stating his belief 

 where it may be an aid to a clearer general 

 understanding of the subject, as in the dis- 

 cussion of the pyrenoid, which he conjectures 

 will prove to be a metabolic center of the 

 chromatophore which is more or less prom- 

 inent according to conditions of nutrition, 

 whose most conspicuous activity is ' the forma- 

 tion of starch by the direct transformation of 

 portions of its substance.' 



In the discussion of direct-cell division the 

 author suggests the possibility that this may 

 be a reversion to early ancestral conditions, 

 mitosis being regarded as phylogenetically a 

 later process. With regard to centrospheres 

 the author recognizes their existence in thal- 

 lophytes only. As to the theory of the per- 

 manence of the chromosome Dr. Davis says ' it 

 can hardly be said that the doctrine is estab- 

 lished.' 



In passing we note that the author regards 

 the Plasmodium of the slime molds as a 

 coenocyte, and further that coenocytes of all 

 kinds are to be regarded as multinucleate cells, 

 and therefore units, instead of compound 

 structures whose cells have not become sepa- 

 rated by walls. 



In the last article (IV,), devoted to cell 

 unions and nuclear fusions, the author draws 

 a sharp line of distinction between those which 

 are sexual and those which are asexual. Un- 

 der the latter (asexual) he includes the fusions 

 of amoeboid cells to form plasmodia, the nu- 

 clear fusions in the teleutospores of smuts and 

 rusts, and the nuclear fusions connected with 

 ' double fertilization.' The remaining articles 

 of this instructive publication will be looked 

 for with keen interest. 



LEAF intumescences. 



In the Sixteenth Annual Report of the Mis- 

 souri Botanical Garden Dr. Hermann von 

 Sehrenk contributes an article on the inter- 

 esting problem of the cause of intumescences 



