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SCIENCE 



[N. S. Vol. XXXIII. No. 842 



abled the investigators to arrive at definite con- 

 clusions, has been the development of a disease 

 propagation garden whereby the struggle for ex- 

 istence of the crop plants against great odds has 

 been carefully noted and the attacking plants 

 observed. 



In summarizing, attention is called to the bear- 

 ings of these findings upon agriculture and upon 

 the various lines of investigation. Proper con- 

 sideration of sanitary methods of handling soil 

 and seed will prove a great boon to cereal crop 

 growers but in order to accomplish this, it may 

 be necessary to rearrange the methods of fertil- 

 izing soils and our systems of crop rotations. 

 These observations regarding the persistence of 

 disease in the seed and in the soil will, of neces- 

 sity, materially change our ideas as to why one 

 crop does better after than before some other 

 crop. These observations, it is thought, explain 

 many of the anomalies of farm cropping: why 

 certain methods of manuring result in shrivelling 

 of seed wheat; why the attacks of rust are so 

 destructive; why proper seed treatment has al- 

 ways resulted in better yields than could be 

 explained by the presence or absence of smut 

 alone; why the corn crop has proved to be such a 

 beneficial crop to precede wheat, etc. 



In closing, attention is called to the extensive 

 work of the Bureau of Soils of the Department 

 of Agriculture upon so-called toxins in the soil; 

 the troubles which they describe may not, of 

 necessity, rest primarily in the soils. Before ma- 

 terial progress is made in the amelioration of 

 conditions of cereal agriculture, proper considera- 

 tion of soil and seed sanitation will prove to be 

 the center about which great modifications in our 

 present methods of agriculture must be shaped. 

 The Succession of Vegetation in Ohio Lakes and 



Ponds: Alfeed Dachnowski. 



Along the line of " watersheds " in Ohio are a 

 number of lakes and ponds in various stages of 

 " filling." Almost throughout, the surface vegeta- 

 tion is one that is common to bogs. In relatively 

 undisturbed areas there is a zonal arrangement. 

 An attempt is made at a classification of the 

 formations, and a formulation of the laws of suc- 

 cession involved in the comparative study. 

 Forest Dynamics on Isle Royale, Lake Superior: 



William S. Cooper. 



The dominant forest of Isle Royale is composed 

 mainly of three tree species — balsam fir, paper 

 birch, white spruce. The relations of these to 

 each other are as follows: Spruce and birch form 

 a small proportion of the forest if all ages are 



considered, but a large proportion of the mature 

 stand. The few large trees of these species are 

 very conspicuous, while young ones are hard to 

 find. Balsams of all sizes, especially small, are 

 exceedingly numerous. The appearance is there- 

 fore of rapid succession, the balsam succeeding 

 the other species. 



Quadrat studies of selected areas, with the ages 

 of all trees in the quadrats determined, shows 

 tnat this appearance is deceptive. The forest as 

 a whole is in equilibrium, but a given area is con- 

 tinually changing in composition and in the rela- 

 tive proportions of the different tree species. The 

 changes are due primarily to the fact that all 

 three species require considerable light during 

 their early stages. One generation in a given 

 area prevents reproduction until maturity or some 

 accidental cause brings about its destruction. 

 Windfall, by allowing light to reach the ground, 

 is the commonest cause of the beginning of a new 

 generation. In windfall areas young tree growth 

 soon springs up, usually predominantly balsam, 

 owing to the ready germination of this species. 

 Balsam never becomes predominant in the mature 

 stand, in spite of high reproduction, because of 

 high mortality. The reproduction of birch and 

 spruce is low, but their mortality is also low. 



The result of these processes is that equilibrium 

 is maintained in the forest as a whole. The dom- 

 inant forest is therefore the Climax Forest of the 

 island. 



Oiservations on the Underground Stems of Sym- 



plocarpus and Lysichiton: C. O. RoSENDAhl. 



The underground stems of Symplocarpus foetidus 

 and Lysichiton camtchatcense are true sympodia, 

 although the fact is not readily perceived on 

 account of their thickness. They grow very 

 slowly, adding only from 3-8 mm. to their length 

 yearly. 



On full-grown plants, five to six renewal shoots, 

 or joints, of the sympodium are produced each 

 year. In Symplocarpus each renewal shoot or 

 joint bears two foliage leaves, a spathe and an 

 inflorescence. In Lysicliiton each joint bears in 

 addition two bracteal leaves, and the last 1-3 

 leaves in the fall are much reduced foliage leaves, 

 i. e., green leaves with very small laminse; in 

 Symplocarpus the first 2-3 leaves to appear in the 

 spring are scale leaves. 



Symplocarpus sends up and matures only 1-2 

 inflorescences a year. The others become arrested 

 and remain in between the broad bases of the 

 foliage leaves. Lysichiton, on the other hand, 

 matures from 2-4 inflorescences yearly. 



