434 



SCIENCE 



[N. S. Vol. XXXI. No. 794 



Wyoming; Winthrop J. V. Osterhout, Harvard 

 University; Robert Boyd Thompson, University 

 of Toronto; and the following members were 

 elected to full membership: C. E. Allen, Univer- 

 sity of Wisconsin; A. F. Blakeslee, Storrs Agri- 

 cultural College; E. J. Durand, Cornell Univer- 

 sity; J. M. Greenman, Field Museum of Natural 

 History, and Shigeo Yamanouchi, University of 

 Chicago. 



Special papers given by invitation of the council 

 were: 



"The Nature of Physiological Eesponse," by C. 

 R. Barnes. 



" The Place of Plant Responses in the Cate- 

 gories of Sensitive Reactions," by F. C. Newcombe. 



" The Distribution of the Vascular Plants of 

 the Gasp6 Peninsula, Quebec," by M. L. Fernald. 



" A Consideration of the Species Plantarum of 

 Linnaeus as a Basis for the Starting Point of the 

 Nomenclature of Cryptogams," by W. G. Farlow. 



The subject for the customary symposium was 

 " Nuclear Phenomena of Sexual Reproduction in 

 Thallophytes and Spermatophytes," and was par- 

 ticipated in by B. M. Davis, who discussed the 

 subject from the standpoint of the algae; R. A. 

 Harper, who considered the fungi; C. J. Chamber- 

 lain, for gymnosperms, and D. M. Mottier, for 

 angiosperms. 



It is expected that all of these papers will be 

 published in The American Naturalist and re- 

 prints distributed to the members of the society. 



Following are abstracts of the papers presented 

 at the two scientific sessions held simultaneously 

 on the afternoon of December 29: 



Botanical Collecting in the Yukon Valley: A. S. 



Hitchcock, U. S. Department of Agriculture. 



By title. 

 Some Evaporation Experiments in Relation to 



Excessive Transpiration: K. M. Wieqand, Wel- 



lesley College. 



In order to determine, if possible, the compara- 

 tive value to the plant of hairy and cutinized 

 coverings, a series of evaporation experiments was 

 made in which cotton or wax spread over an evap- 

 orating surface of saturated blotting paper were 

 substituted for a hairy leaf or a cutinized leaf, 

 respectively. Comparative readings of the loss of 

 water from the variously treated blotting papers 

 in still air and in wind were made, with the fol- 

 lowing results: the evaporation was retarded 

 much more by the wax than by the hair; the effi- 

 ciency of the hair, however, was much greater in 

 wind than in the quiet, and even very thin hairy 



coverings produced a noticeable retarding effect 

 in wind. In sunshine the retarding effect was also 

 marked. Plants might therefore be supposed to 

 make use of waxy coverings when transpiration 

 is to be retarded at all times, and hairy coverings 

 when it is to be retarded only if exposed to strong 

 dry winds and sunshine. 



The Responses of the Guayule, Parthenium argen- 



tatum Gray to Irrigation: Feajstcis E. Llotd, 



Alabama Polytechnic Institute. 



A brief summary of the more important results 

 of a study of the guayule, Parthenium argentatum 

 Gray, under irrigation at Cedros, Mexico, for a 

 period of two years, touching (1) the rate of 

 growth, (2) the anatomical changes which ensue 

 and (3) the rate and amount of rubber secretion 

 together with a discussion of centers of secretion. 



Guayule under irrigation makes an annual 

 gr wth up to 25-30 cm. stem length, which ap- 

 pears to be approximately the maximum rhythmic 

 response. Field plants in the same region make 

 an average growth of 3 cm. Guayule responds 

 readily, therefore, to irrigation, making plants of 

 two to three pounds in weight from closely pol- 

 larded stocks. 



At the close of two seasons' growth in August, 

 1908, irrigated plants showed only minute quan- 

 tities of rubber. The same plants in the following 

 April showed a large though not a maximum 

 amount. Still more was found to occur in plants 

 which had received less water of irrigation, this 

 in growths of 1908 and 1909, in October, 1909. 

 The conclusion is arrived at that, though the rate 

 of secretion is slower in more rapidly grown 

 plants, it may, after drought, approach fairly 

 closely, if not entirely, to the maximum. The 

 behavior under irrigation may be regarded as the 

 behavior in feral plants with an exaggerated time 

 element. In view of the total amount of growth, 

 however, the conclusion that a total amount of 

 secretion in an irrigated plant is greater in the 

 long run than in a field plant is justified. 



it is further shown that marked anatomical 

 changes result from irrigation, chiefly affecting 

 the volume of the cortex which is reduced under 

 irrigation. The volume of the medullary rays is 

 also much less, and sclerosis overtakes the medul- 

 lary rays cells and sometimes the pith cells. The 

 effect upon the amount of rubber is apparent in 

 view of its distribution in these tissues, and not 

 in the xylem and phloem (the parenchyma of these 

 excepted ) . 



The rubber is secreted from the secreting cells 



