938 



SCIENCE 



[N. S. Vol. XL. No. 1043 



dripping point, the velvet surface, the varie- 

 gated leaf, drooping juvenile foliage, etc." 

 Upon some of these structures his comments 

 are suggestive, as. 



There is no feature of foliage leaves that ap- 

 pears to give greater promise of having concrete 

 utility under rain-forest conditions than does the 

 hydathode. 



Tet in his summary he says : 

 Plants possessing hydathodes are very infre- 

 quent in the montane rain forests of Jamaica. 



So, too, he says : " Plants possessing dripping 

 points are relatively uncommon in the rain- 

 forest," and a little later, " Surface wetness 

 does not lower the temperature of leaves 

 sufficiently, under rain-forest conditions, to 

 affect their transpiration rate." 



The paper is so full of interesting results 

 that it is quite impossible to summarize it as 

 a whole, yet one rises from reading it with the 

 feeling that it must do much to correct current 

 notions as to the ecology of tropical leaves. 



NORTH AMERICAN FLORA 



Part 1 of Volume 29 of this slowly moving 

 publication appeared August 31, 1914. It con- 

 tains the following families of the Order 

 Ericales: Olethraceae by N. L. Britton; Mono- 

 tropaceae, by J. K. Small ; Lennoaceae, by P. A. 

 Eydberg; Pyrolaceae, by P. A. Eydberg, and 

 Ericaceae, by J. K. Small. In the last-named 

 family the genus Arctostaphylos, now named 

 JJva-ursi, is treated by LeEoy Abrams. 



PERENNIAL GRASS STEMS 



In a recent paper on the "Development of 

 the Culms of Grasses " (exclusive of Bamboos) 

 by E. S. Hole, of the Imperial Forest Service 

 of India,^ is a paragraph which will be of in- 

 terest to many a botanist: 



It is a common belief, probably due to a study 

 of the species characteristic of temperate coun- 

 tries, that the culms of grasses are annual, i. e., 

 that they start growth, attain maturity and ripen 

 grain in a period not exceeding twelve months. 

 In some, at least, of the species of considerable 

 economic importance which are dominant in the 



2 Forest Bull. 25, Calcutta, 1914. 



Savannah lands of our Indian forests this gen- 

 eralization does not hold good. In Saccharum 

 munja Eoxb. the culms are, as a rule, biennial, 

 and a number of culms of Saccharum arundi- 

 naceum Eetz. are now under observation in the 

 Dehra Experimental Garden which are two years 

 old and which, although still growing vigorously, 

 have not yet attained maturity. 



No doubt other cases of perennial stemmed 

 grasses may be found by a little searching. A 

 woody-stemmed south Florida grass (Panicum 

 latifo'Uum L.) appears to have a stem which 

 continues to grow for more than one year. 



SOME TEMPERATURE RELATIONS OF PLANTS 



Several paragraphs in Dr. Shreve's paper 

 on " The Eole of Winter Temperatures in 

 Determining the Distribution of Plants "' are 

 distinctly quotable, and at the same time help- 

 ful to a better understanding of some of the 

 temperature relations of plants. As to phenol- 

 ogy and phenologists, he says: 



More attention has been given by phenologists 

 to the temperature phases of the growing season, 

 and their potentialities, than to those of the frost 

 season. . . . The gigantic toil of the phenologists 

 between 1850 and 1890 yielded some results on 

 the operation of temperature, and gave us a vast 

 accumulation of data of which some real use was 

 made at the time, and to which we may return in 

 future investigations. . . . Their efforts were 

 handicapped by the fact that they worked exten- 

 sively rather than intensively, and that they had 

 not a sufficient foundation of physiological facts 

 upon which to operate. 



The viewpoint of the geographer — and with him 

 that of many floristic plant geographers — is too 

 broad and general to give due regard to the ac- 

 tual physiological effects of temperature on 

 plants; the point of view of the plant physiolo- 

 gist, on the other hand, is often too intensive to 

 enable him to realize that the ' ' conditions ' ' of 

 his laboratory experiment are identical with the 

 "physical factors" of the environment of plants 

 growing under a state of nature, and he is there- 

 fore prone to neglect the bearing of his work on 

 the problems of the field. 



From his point of view Dr. Shreve very 

 properly criticizes the system of life zones pro- 

 posed by Merriam, concluding that 



3 Am. Jour. Bot., No. 4, 1914. 



