220 ECOLOGY, PLANT GEOGEAPHY [Bot. Absts., Vol. VI, 



4, Entry 196). This forest is regarded as the climax type for a large portion of the adjacent 

 country. A biological spectrum of the Raunkiaer type would show an enormous preponder- 

 ance of woody plants arranged in three distinct strata, the ground cover being comparatively 

 bare of herbaceous vegetation. There is a great diversity of species, with the Leguminosae 

 as the most prominent family and the Rubiaceae and Piperaceae particularly abundant 

 among the shrubs. Ferns and lycopods are largely limited to rocky spots. Conspicuous and 

 highly colored flowers are abundant in the upper canopy and notably lacking below. But- 

 tressed tree trunks are rare in spite of the frequency of .violent winds but thorny stems are 

 frequent even in large trees. The floristic diversity and the contrasting uniformity of 

 appearance especially in leaf form are ascribed to (1) the antiquity of prevailing conditions 

 and (2) the peculiarity of the environment. The soil is shallow and pervious, with a water 

 holding capacity of about 40 per cent and an average water content of 10 per cent. It ia 

 deficient in mineral nutrient material, particularly in calcium carbonate. The humus con- 

 tent is about 3 per cent. Mycorhiza is very abundant. A very considerable amount of 

 rain is intercepted by foliage and evaporated into the air, thus reducing the rainfall efficiency. 

 Light measurements made with photographic exposure meters show the average ratio of the 

 light outside and that within the deep forest to be 1 : 0.06; some spectroscopic measurements, 

 however, tend to show that the photosynthetic efficiency of the shade illumination is rela- 

 tively greater than the actinic. — The leaves of the forest are in general characterized by their 

 large size, the small number per plant, and the frequency of nyctitropic movements and of 

 vertical position. The shade leaves show conspicuous water storing epidermis, reduced and 

 undifferentiated mesophyll and occasional epidermal papillae. The leaf area of the sun 

 foliage is approximately the same as that of the shade leaves, but the latter are decidedly 

 larger and narrower. Red coloration is common in the young shade leaves, and such leaves 

 are shown to have a higher rate of respiration. The percentage of carbon dioxide within the 

 forest is shown to be high, and here light is doubtless the limiting factor of photosynthesis. 

 —Geo. D. Fuller. 



1501. Watt, A. S. On the causes of failure of natural regeneration in British oakwoods. 

 Jour. Ecol. 7: 173-203. 1919. — The investigation was conducted in the vicinity of Cambridge 

 England, and the report is presented in three parts, dealing respectively with the acorn, 

 its germination, and the seedlings. The rapid disappearance of even a large crop of acorns 

 from the forest floor is seen to be largely due to the action of rabbits and mice. The drying 

 of the acorn to an extent that results in the loss of 20 per cent of its water is found to prevent 

 subsequent germination. Experiments were conducted to discover the amount of imbedding 

 in the soil necessary for good germination, and in general it was found that at least one-half 

 of the nut should be below the surface; on the other hand burial to depths ranging from 3 

 to 9 inches in sandy or clay soil gave equally good germination. Rabbits, mice, and larger 

 grazing animals are shown to destroy very large percentages of the seedlings during the first 

 few years of their existence. One of the mildew fungi proved rather destructive, especially 

 on the sandy soils. Emphasis is placed on the fact that by destroying carnivorous animals 

 man has upset the balance of nature and favored the enemies of forest regeneration. The 

 chances of good regeneration decrease on passing from the "damp oak association" to the 

 "dry oak association," and from the latter to the "oak-birch heath." — Geo. D. Fuller. 



STRUCTURE, BEHAVIOR 



1502. Betts, M. Winifred. Notes on the autoecology of certain plants of the Peridotite 

 Belt, Nelson [New Zealand]: Part I. Structure of some of the plants (No. 2). Trans, and 

 Proc. New Zealand Inst. 51 : 136-156. 27 fig. 1919. — The region studied is about thirty square 

 miles in area, with a vegetation of xerophytic shrubs and grassland. A detailed description 

 is given of the growth-forms, and of the anatomy of the leaf and of the stem, of fifteen char- 

 acteristic plants. — L. W. Riddle. 



