152 CARNEGIE INSTITUTION OF WASHINGTON. 



"Results recently obtained by other investigators on the distribution of 

 injected manganese dioxide in the fowl also seem to invite the suggestion 

 that, in pigeons, the organs which probably remove most of such finely 

 divided non-living particles and most infecting bacteria from the blood- 

 stream are the organs most often infected by tuberculosis. 



"The ovary is probably more often infected than is the testis in most 

 groups of pigeons; in domestic or common pigeons the data indicate an equal 

 susceptibility of ovary and testis to this infection. 



"The organs of hybrid birds derived from different genera are probably 

 not changed in their relative susceptibility to tubercular infection by the 

 mere fact that these organs are of hybrid origin. 



"In addition to a possible contribution to our information concerning the 

 localization of the attack of the tuberculosis bacillus, and also to our con- 

 ception of phagocytosis, two points of more immediate relation to my own 

 field are indicated by this study. First, the probability that the ovary is 

 more susceptible than the testis to tuberculous infection in pigeons other 

 than common pigeons, but equally susceptible in the latter forms, may prove 

 to be of significance in the theory of sex. Second, the present incomplete 

 story of the effects of hybridization is perhaps none the more incomplete 

 because of the observation that the organs of hybrid birds derived from 

 different genera are probably not changed in their relative susceptibility to 

 tubercular infection by the mere fact that these organs are of hybrid origin." 



Studies on Physico-Chemical Properties of Vegetable Saps. 



The problem of the adjustment of parasitic plants to the conditions 

 presented by the host. — Dr. Harris has continued the investigations on 

 the evolution of loranthaceous parasites, which have been under way 

 for the past several years. Harris and Valentine have shown (Proc. 

 Soc. Exp. Biol. Med., 18 : 95-97) that the specific electrical conductiv- 

 ity of the tissue fluids of the parasite are higher than those of the host. 

 Harris, Lawrence, Hoffman, Valentine, and Mrs. Lawrence are now en- 

 gaged on further studies of the electrical conductivity and hydrogen- 

 ion concentration of the tissue fluids of Phoradendron and its hosts 

 in the Gila River Valley, Arizona. 



Physico-chemical properties of the tissue fluids of alpine and sub- 

 alpine vegetation. — Through the courtesy of Professor F. E. Clements, 

 Associate in Ecology of the Carnegie Institution of Washington, it 

 has been possible for Dr. Harris to extend the work on the physico- 

 chemical properties of plant-tissue fluids in relation to environmental 

 factors and geographic distribution to include the alpine and subalpine 

 vegetation of the Pike's Peak region of Colorado. Mr. and Mrs. 

 John V. Lawrence devoted some weeks to measurements of osmotic 

 concentration, specific electrical conductivity, and hydrogen-ion con- 

 centration at Professor Clement's Alpine laboratory during the sum- 

 mer of 1921. 



Physico-chemical properties of coastal vegetation. — For the past 

 several years studies of the sap properties of coastal vegetation in 

 their relation to the adjustment of the species to various salinities 

 have been under way. Extensive series of determinations have been 

 made in the neighborhood of Cold Spring Harbor (Long Island), 



