SCIENCE-GOSSIP. 



65 



the opinion that at no time has scientific 

 collection caused the extinction of any species ; 

 neither has the senseless shooting of odd indi- 

 viduals of anv kind of birds by casual fowlers 

 exterminated their species. Perhaps two avoid- 

 able agencies may have contributed to hastening 



the end of some, namely, the acquisition of 

 birds for purposes of ladies' millinery, and the 

 unmeaning rage among collectors for "British" 

 specimens of species common on the other side of 

 the English Channel, whence they are frequently 

 blown over to our shores. 



VEGETABLE NATURE OF DIATOMS. I 1 ) 



By T. Chalkley Palmer. 





T"HE essentially vegetable nature of diatoms 

 is at the present time acknowledged by 

 biologists almost or quite without exception. 

 The phenomena of their increase and reproduction, 

 if nothing else, are of a nature to call for their 

 grouping in the same class with such undoubted 

 plants as desmids and the Zygnemaceae. Yet 

 every young student, 

 seeing for the first 

 time the glassy cells I 



of diatoms moving 

 about under his mi- 

 croscope in a manner 

 that would seem to 

 indicate a very ani- 

 mal-like volition, is 

 liable to ask for 

 some tangible proof 

 of their plant nature. 

 some more elemen- 

 tary argument than 

 that drawn from re- 

 lations which are to 

 be apprehended in 

 all their significance EZ 

 only after somewhat / 



extended study. 



ever difficult, or even impossible, it may be 

 lo draw a definite line that shall separate the 

 animal and vegetable kingdoms, it is probable that 

 no one will object if the term " plant " is applied 

 lo an organism which, when exposed to sunlight, 

 is found to absorb carbon -dioxide and to exhale 

 oxygen The method and apparatus described 

 herein arc designed I that both these 



phenomena, which arc so characteristic of plants 

 in general, arc charar-'' itom Pelletan 



(" Les Diatomcs ") Mates that he has collected 

 sufficient of the gas ari- ring from dial 



■ usual chemical te its 

 which prove it f I'.iit ii i . not • 



bring together • :.it the 



collection, from diatoms alone, of such a volume 

 of gas as is rc|uir- derablo 



time, also, must be needed fbi 



to the 

 . ,,. . 



X 



A 





n 



success of the experiment ; for in the absence of 

 sunshine, or at least of bright daylight, it is found 

 by experience that diatoms, and especially the 

 motile forms that are expending energy in the way 

 made evident by their motion, cease to exhale 

 oxygen and begin to absorb it, or at least to give 

 out carbon-dioxide. This phenomenon — the 



evidence of an ex- 

 othermic chemical 

 reaction — the dia- 

 toms exhibit in com- 

 mon not only with 

 animal organisms, 

 but with all plants 

 also. It is the well- 

 known process of re- 

 spiration, that which 

 Gautier has called 

 " the animal life of 

 plants." The method 

 I desire to describe 

 isof great simplicity, 

 and it yields con- 

 clusive results within 

 an hour, provided 

 i.m 1 J. Nature 01 Diatoms. the light be suffici- 



ently strong; it does 

 not necessitate the collection of any appreciable 

 volume of gas, and it demonstrates both phases of 

 the endothermic reaction. 



Haematoxylin, the chromogen of logwood, is 

 peculiarly fitted to be an indicator in a case where 

 it is desired to recognize the presence or absence 

 of carbon-dioxide and the evolution of nascent 

 1, the solvent being ordinary water from 

 spring or river containing its usual traces of 

 various mineral matters. Under the influence of 

 1 dioxide, ihe haematoxylin dissolved in such 

 water loses its normal rosy or slightly bluish-red 

 tint, and mrn-, to a yellow with a tinge of brown. 

 in the presence of nascent oxygen, on iin- oth.-r 



'lie ligl I Inn- il, i-|„-iis momentarily. 



;i "'l ends bj becoming a very deep bl l-red. 



1 he latter 1 bange i-. in a mat 1 permanent, 



but the form.-, 1 . revci Ible, the rosy. red 

 colour return-, when the 1 arbon dioxide ii 

 removed The* well-known coloui reai is are 



7 ZT\ 



i> 2 



