56 ECOLOGY, PLANT GEOGRAPHY [Bot. Absts., Vol. IV, 



to be placed at thousands rather than at scores of years. The dominant plants point to the 

 existence of two habitats, one xerophytic and the other mesophytic. An area of upland dis- 

 sected by a valley furnishes such habitats and at the same time meets the geological require- 

 ments of the formation. [See Bot. Absts. 1, Entry 1603.]— Geo. D. Fuller. 



375. Clements, F. E. Scope and significance of paleo-ecology. Bull. Geol. Soc. Amer. 

 29: 369-374. 1918. — The article is a general statement of the scope and character of paleo- 

 ecology and of some of the results that may be hoped for from its application to some of the 

 problems of geology. The conclusions are summarized by the author in the statement that 

 "Paleo-ecology is characterized by its great perspective, due to the absence of a large body 

 of facts. This causes the fundamental correlations between the physical world and vegetation 

 on the one hand and between vegetation and the animal world on the other to stand out in 

 clear relief. As a consequence, paleo-ecology is an unspecialized field in which the inter- 

 relations of climate, vegetation and animals play the paramount role. The emphasis neces- 

 sarily falls on vegetation, because it is an effect of climate and topography, and a cause in 

 relation to the animal world, and hence serves as a keystone in the whole arch of cause and 

 effect." [See Bot. Absts. 1, Entry 1604.]— Geo. D. Fuller. 



376. Guppy, H. B. The island and the continent. Jour. Ecol. 7: 1-4. May, 1919.— Re- 

 ferring to Hooker's discussion of insular floras the author agrees with him that islands have 

 been the refuges of the ancient vegetation of continents. On the Micronesian Islands in par- 

 ticular he sees the wrecks of a very ancient flora once more widely spread and flourishing in 

 the warmer and moister Tertiary period but expelled and largely destroyed during a succeed- 

 ing age of aridity. Australia is regarded as giving the plant record of lost eras of much of the 

 globe and Madagascar as recounting the tale of lost ages in the tropical zone. The question 

 of continental connections is regarded as a dead issue and the distribution of conifers is ac- 

 cepted as the best guide to past continental extensions. — The article is rather a general state- 

 ment of the situation under discussion than a contribution of fresh data regarding the charac- 

 ter of insular floras. — Geo. D. Fuller. 



377. Holmsen, Gunnar. Lidt om grangransen i Famundstrakten. [Norway spruce in 

 Famund, Norway.] Tidsskr. Skogbruk 27: 39-48. Mar.-Apr., 1919. — It has been a generally 

 accepted theory that Norway spruce reached Norway from Russia by way of Finland and Swe- 

 den, that sufficient time has not yet elapsed for it to cover every nook and corner of the coun- 

 try as shown by the present distribution. The author has endeavored to throw light on this 

 question by a microscopic study of pollen in old swamp deposits. Pollen grains of spruce 

 have thus been readily identified when present. Though there remain many unsolved prob- 

 lems, this study indicates strongly that spruce is no younger on the peninsula than the other 

 forest trees. It appears that the immigration of spruce took place toward the end of the sub- 

 boreal or in the early sub-atlantic era and that spruce appeared earlier in the northern and 

 eastern part of Sweden than elsewhere. — J. A. Larsen. 



APPLIED ECOLOGY 



378. Kincer, Joseph B. Temperature influence on planting and harvest dates. Monthly 

 Weather Rev. 47: 312-323. Fig. 1-20. 1919.— There are certain restricted limits of time 

 within which crops must be planted for best results, defined by the temperature conditions of 

 the locality. In general the length of the time period for planting decreases with increase in 

 latitude. — A definite amount of heat is required after planting to bring a crop to maturity; 

 one may take as a rough measure of this the accumulated day-degrees of temperature above 

 the mean temperature at planting time. As thus computed there is very little difference in 

 the amount of heat necessary to mature most staple spring planted crops. The mean temper- 

 ature at planting time for a given crop may be used as a base for any method of temperature 

 summation for that crop, but not as a general base for all crops. If the frequently used 6°C. 

 base be employed in the case of cotton, for example, we would begin the reckoning of effective 



