AGRICULTURAL BOTANY. 423 



Au attempt was made to estimate the magnitude of the cooliug due to trans- 

 piration, and differences averaging 2.5° were determined in leaves having their 

 stomata so arranged as to give different exposures. . 



The principal factor tending to reduce high temperature reached in sunlight 

 was found to he the movement of the air, and breezes of various strengths 

 were found to reduce the temperature attained in the sunlight from 2 to 10°. 



Red leaves attained a higher temperature than white or pale leaves of the 

 same thickness and texture, and immature thin colored leaves of various trop- 

 ical ti'ees may have either higher or lower temperatures than thick green leaves 

 of the same species. This difference is believed to be due to the amount of 

 anthocyanin in the leaf. 



In the second part of the paper an account is given of observations made at 

 intervals of a number of trees showing new growth, the leaves of which were 

 sharply differentiated as to their color from the mature leaves. It was found 

 that the new growth was most prevalent in the driest season and almost ab- 

 sent in the wettest months, and it is suggested that probably in a climate of 

 high humidity it is only during the dry period that a sufficient transpiration 

 stream is obtained to supply the large amount of mineral substances required 

 in the formation of the new gi-owth. If this should be true, the higher internal 

 temperatures attained by the coloration of young leaves would also promote an 

 increase in the transpiration stream, 



A bibliography of publications relating to the subject completes the report. 



Studies on Plasmodiophoraceae and Phytomyxinse, R. Maire and A. Tison 

 (Ann. MycoL, 7 (1909), No. 3, pp. 226-253, pis. 3, fi(j. i).— A study was made of 

 a number of plants belonging to the Plasmodiophoraceae, a type of which is 

 Plasmodiophora brassiccr, and also of species of uncertain affinities which have 

 been variously referi'ed to this group and to the Phytomyxinne. The species 

 studied include Sorosphccra veronicw, PUismodlophora brassicce, Tetramyxa 

 parasitica, Phytomyxa Icguminosurum, Plasmodiophoni aliii, Plasmodiophora 

 elwagni, Tylogonus agarw, and Pscudocoinmis litis. 



The authors state that 8. veronicw is not a filamentous fungus, as has been 

 claimed, but belongs to the Plasmodiophorace;e. This species and P. brassicw 

 represent two phases, a schlzogenous and a sporogenous. The group to which 

 these are referred should, the authors claim, be considered entirely independent 

 and as intermediate between the Sporozoaires and Myxomycetes. P. alni and 

 P. ela'agnl do not belong to this family but are Schizomycetes and should be 

 grouped together under the generic name Frankiella. Likewise the organism 

 living in symbiosis in the root tubercles of leguminous plants is a Schizomycete, 

 the proper name for which would be Phytomyea Icguminosaruni. T. agavce 

 and Pseudocommis spp. are not true organisms but are the results of degenera- 

 tion of the cell contents. 



The action of poisons on Chlamydomonas and other vegetable cells, H. W. 

 Harvey (Ann. Bot. [London], 23 (PJ09), No. 90, pp. 181-187, dgms. 2).— The 

 toxic action of dilute solutions of the isomers of various benzene derivatives 

 upon Chlamydomonas has been studied, and the author determined the minimal 

 concentrations required to cause cessation of movement in a culture of actively 

 motile C in iilti fills in 10 minutes. Comparisons are given showing the effect of 

 these poisons on the root cells of white lupine and bacteria. 



The results are tabulated and show that* there is a similar reactivity of the 

 different vegetable cells toward the same poison, and also a fairly constant 

 relation between the chemical constitution of a poison and its toxic strength. 

 The chemicals used in these experiments were orthodihydroxy-phenol, metadi- 



9049— No. 5—09 3 



