324 



SCIENCE 



[N. S. Vol. XLIII. No. 1105 



the Eoeky Mountains, where five formations occur, 

 namely plains grassland, woodland, montane forest, 

 subalpine forest and alpine grassland. Finally, 

 while each climax is more or less stable during a 

 climatic period, the transition between two cli- 

 maxes bears eloquent testimony to the shiftings 

 of dominants and subdominants produced by minor 

 climatic cycles. 

 A Photometer Battery for Habitat Analysis: P. 



E. Clements. 



A series of photometers has been devised for the 

 comprehensive study of the intensity and quality 

 of light in the various kinds of habitats. Those 

 used to measure light intensity are based upon the 

 Bunsen-Eoscoe photographic method. The simple 

 photometer is designed for use on reconnoissance 

 trips or in connection with a base station. Its 

 most desirable form is the stop-watch photometer 

 in which the personal factor in timing is elimi- 

 nated. It is further modified into the water pho- 

 tometer for securing light readings at various lev- 

 els in ponds and lakes. The recording photometer 

 or selagraph consists essentially of a clock mechan- 

 ism and a photographic shutter, permitting hourly 

 exposures for a week without attention. The elec- 

 tric spectro-photometer is a compact instrument 

 for determining the light quality in forest and 

 thicket or at different altitudes, without the use 

 of a tripod. 

 What is Tolerance of Forest Trees? George P. 



Burns. 

 The Boot Growth of Forest Trees: W. B. Mc- 



DOTJGALL. 



Direct observations were made on the roots of 

 Acer saccharinum, Tilia americana, Carya alia 

 and Quercus macrocarpa, nearly every week dur- 

 ing the growing season and occasionally during 

 the winter, from April, 1914, to September, 1915. 



Growth begins in April, the exact time varying 

 with the season. It ceases in autumn or early 

 winter when the soil becomes too cold for absorp- 

 tion. In 1914 there was a resting period of about 

 five weeks in July and August when no root growth 

 occurred. During this time the soil was very dry. 

 In 1915 there was no dry season and no resting 

 period. No attempt has been made to determine 

 accurately at what temperature growth ceases or 

 how much soil moisture is necessary for growth, 

 but it is believed that enough has been done to 

 establish the following general facts: (1) The root 

 growth of forest trees begins as early in spring as 

 the soil becomes warm enough for absorption, and 



ceases in autumn when the soil becomes too cold. 

 (2) There is not necessarily a summer resting 

 period. (3) When there is a summer resting 

 period it is due to a lowering of the water supply, 

 and not to any inherent tendency toward periodic- 

 ity. 



The Marine Algae of Beaufort, N. C, and Adjacent 



Segions: W. D. Hoyt. 



Contrary to the belief that the Atlantic coast 

 from Long Island to Florida is barren of Algae, 

 138 species and varieties have been found, all ex- 

 cept 10 of these occurring at Beaufort. Of the 

 total number, 130 have been obtained in sufficient 

 amount for determination. There are represented 

 83 genera and 34 families, including aU four di- 

 visions of Algae. The identified species are dis- 

 tributed as follows: Myxophyceae, 10, 7.7 per 

 cent.; Chlorophyceae, 25, 19.2 per cent.; Phaeophy- 

 ceae, 27, 20.8 per cent. ; . Ehodophyceae, 68, 52.3 

 per cent. Because of its intermediate position, 

 Beaufort has an algal flora of unusual interest, 20 

 genera and 41 species reaching here their north- 

 ern known limit on our coast, while 3 genera and 

 9 species reach here their southern known limit. 

 Eighteen species new to North America have been 

 found, 8 of these being hitherto undeseribed. The 

 seasonal differences are strongly marked in the 

 flora of Beaufort harbor, only 12 species having 

 been found throughout the year and 4 others in 

 both spring and summer. The appearance and dis- 

 appearance of the seasonal floras are strikingly 

 coordinated with the observed temperature of the 

 water. Measurements of the light show that this 

 penetrates to very slight depths. Correlated vrith 

 this fact, the algae seldom extend to a depth 

 greater than 90 cm. below the low tide line. With 

 the exception of a very few species, no Algae are 

 found in summer above the low-tide mark. Sev- 

 eral submerged coral reefs lying offshore offer 

 extremely interesting conditions and a very in- 

 teresting flora resembling that of subtropical re- 

 gions. 



Endemism in the Flora of the Vicinity of New 



Torlc: Norman Taylor. 



Endemism, as found in the flora of the vicinity 

 of New York, does not appear to be a criterion of 

 antiquity, for many endemics are very recent. 

 Neither are the endemics prevailingly woody, for 

 only 4 woody forms out of a total endemic element 

 of 22 species disproves this contention. Nor does 

 antiquity or woodiness prevail among the species 

 of endemic genera. Rarity or commonness does not 



