338 



SCIENCE 



[N. S. Vol. LIV. No. 1397 



from 4.2 to 11. Effects as of balanced solutions 

 were obtained with agar, and suggestions of sim- 

 ilar action with agar-gelatine-salt mixtures. The 

 ineorporation of nutrient salts in agar and biocol- 

 loids in minute proportions such as might occur 

 in plants increased the swelling capacity of some 

 mixtures, in contradiction to earlier announcements 

 by the author. Roots of various plants showed 

 special effects in swelling, and also variations 

 according to the ecological type of these organs. 

 Such differences are determined by the composition 

 of the cell-colloids. Finally the facts confirm an 

 earlier statement to the effect that all substances 

 known to facilitate growth of plants accelerate 

 hydration of growing tissues, and of biocolloids 

 simulating their protoplasm when used in low con- 

 centrations equivalent to those in which they are 

 usually encountered by living matter. 



Growth of trees: D. T. MacDougal. Extended 

 measurements of the growth of many trees of a 

 number of species have been made by the use of 

 the newly designed dendrograph, which makes a 

 continuous record of changes in diameter, and the 

 recently perfected dendrometer, which registers 

 total change in circumference. It is found that the 

 period during which growth takes place even in 

 equable climates with indeterminate seasons does 

 not extend over more than two or three months, 

 and that growth is not rhythmical in any sense, 

 but depends upon food-supply, temperature, mois- 

 ture and other environmental conditions. Awaken- 

 ing of buds, formation of leaves and flowers, and 

 elongation of branches may occur many days or 

 even weeks before trunks begin to enlarge. The 

 leaves of a beech tree in Baltimore began to unfold 

 April 10, 1919, and enlargement of the trunk began 

 about May 18. Daily equalizing variations by 

 which a tree may be actually smaller in mid-after- 

 noon than at sunrise are greatest in the ash, pine, 

 spruce, fir and walnut, and least in poplars, syca- 

 more, beech and oak trees. Accurate measurements 

 of the changes in trunks internal to the growing 

 layer show that these variations are directly con- 

 nected with the mechanism of the ascent of sap and 

 are explainable upon the assumption of a rigid 

 water column in a trunk composed of wood-cells 

 and vessels capable of some shrinkage and expan- 

 sion. Crudely expressed the trunk behaves like 

 a heavy hose feeding from a pressure system to a 

 fire engine. When the engine tends to take wat^r 

 faster than supplied, the hose tends to collapse; 

 when the engine slackens its action, the hose swells. 



Fishes of Ecuador and Peru: Cakl H. Eigen- 



MANN. The fishes of the Guayas basin on the 

 Pacific slope of Ecuador and those of the rivers 

 of Chile are completely different in species. Even 

 the genera with the exception of the mountain cat- 

 fish Pygidium are all different. Excluding the 

 marine fishes even the families and orders of fishes 

 in the two areas are largely different. The differ- 

 ences between the two faunas are so great there is 

 not a shadow of a doubt that in the main their 

 origins were different. The Chilenian fishes came 

 from the south. The Guayas fishes came from the 

 Amazon. The Pacific slope of South America be- 

 tween Panama and Patagonia varies in width from 

 a few yards in Colombia, west of the Atrato river, 

 to a hundred miles or more. The slope is extremely 

 wet in Panama and Colombia, varies from wet in 

 the north of Ecuador to dry in the south of 

 Ecuador. The slope varies from dry in northern 

 Peru to very dry in southern Peru, and almost if 

 not absolutely dry in Chile, south of Copiapo. The 

 Guayas basin drains the area between a coast range 

 and the Cordilleras of central Ecuador. The 

 Guayas has the distinction of being the only river 

 with a flow in the main parallel to the Andes. All 

 the other Pacific slope rivers between the equator 

 and Cape Horn (with the exception of the Rio 

 Santa) flow direct from the Andes westward to 

 the Pacific. The Guayas basin is the largest river 

 basin draining into the Pacific between the equator 

 and southern Chile. The rivers grow smaller south 

 of Ecuador to northern Chile. A stretch of over 

 500 miles in northern Chile is crossed by but one 

 river, the Loa. The first river south of the great 

 desert of Atacama is the Rio Copiapo. I fished 

 from Copiapo southward through central Chile over 

 a stretch nearly a thousand miles long. The gen- 

 eral conclusion reached is that the fauna of Chile 

 is at its height between Concepoion and Yaldivia. 

 Going north from Valdi^'ia one genus after another 

 disappears. Aplochiton^ a trout-like genus of Aus- 

 tralia and Chile and Galaxias, another genus of 

 Australia and Chile, reach their farthest north in 

 the Bio Bio. The peculiar catfishes Dyplomyste 

 and Nematogenys reach their farthest north in the 

 Maipo. Percichthys reaches the Aconcagua. North 

 of the Aconcagua in the region of the extinct or 

 dying rivers but three species of the Bio Bio fauna 

 remain : a " peje rey, ' ' Ba-silichthys, the ubiquitous 

 catfish Pygidium and Cheirodon. The little Cheiro- 

 don whose ancestors have come from tropical Brazil 

 I caught as far north as Vallenar. In the Copiapo 

 I caught no native fishes. The peje rey extends all 

 the way to Lima, Peru. 



