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



structure, as indicated by specialized palisade tissue, water storage tissue, and a thick-walled 

 epidermis, with or without trichomes. Xerophytism, however, is indicated not so much 

 by these characters taken alone as by their correlation with other features, such as extensive 

 root systems. Upland plants have a thinner epidermis than have lowland plants. 75 per 

 cent of the upland species have trichomes, while 70 per cent of the lowland species are without 

 them. 50 per cent of the lowland species have bifacial leaves, while but 33 per cent of the 

 upland species possess them. Half of the upland species have centric to subcentric leaves, 

 while only 12.5 per cent of the lowland species may be so classed. [See Bot. Absts. 2, Entry 

 978.]— H. C. Cowles. 



228. Hayden, Ada. The ecologic subterranean anatomy of some plants of a prairie 

 province in central Iowa. Amer. Jour. Bot. 6: 87-105. 14 pi. Mar., 1919. — Subterranean 

 organs were studied in 26 species of prairie plants, 15 being upland species, and 11 species of 

 alluvial basins. In the upland species there is a tendency to the production of prominent 

 mechanical tissue; except in a few cases (as in Spartina Michauxiana and Panicum virgatum) 

 mechanical tissues are moderate or lacking in the lowland species. In general parenchyma- 

 tous tissue is reduced in the upland species and prominent in the lowland species, aerenchyma 

 being present in the swamp plants. Vascular tissue appears to vary more taxonomically than 

 ecologically. Subterranean stems tend to predominate in moist lowlands as an equivalent 

 of primary roots and are more efficient than roots in propagation. The stem pith serves as 

 a water reservoir. [See Bot. Absts. 2, Entry 745.] — H. C. Cowles. 



229. Heintze, Atjg. Till kannedomen om Potentilla multifidas spridningsbiologi. [The 

 distribution biology of Potentilla multifida] (Swedish). Bot. Notiser 1918: 302-206. 1918 — 

 Records of occurrence of this species are given from Graubunden and the East Alps. In the 

 Alps it is evidently distributed by sheep, chamois, and other animals. It was probably car- 

 ried to the Alps by reindeer-raven. In an appendix, the author enumerates several other 

 species, which spread from seeds passed through the intestines of animals. — P. A. Rydberg. 



230. Heintze, Aug. Om endo- och synzoisk frospridning genom europeiska krakfoglar 

 [Endo- and syn-zoic dispersal of seeds by European Corvidae]. (Swedish.) Bot. Notiser 1917: 

 209-240. 297-300; 1918: 1^17. 1918.— The studies include the following birds: Pica pica, 

 Corvus cornix, C. corone, C. frugilegus, Coloeus monedula, Corvus corax, Pyrrhocorax pyrrho- 

 corax, P. graculus, Cractes infaustus, Nussifraga caryocactes, and Garrulus glandarius. Nearly 

 all of these distribute plants which bear berries or stone-fruits. The seeds or stones of these 

 are not at all or only partly damaged in the crop. All the larger, most of the middlesized, 

 and half of the smaller seeds or fruits are dispersed in a hemi-endozoic way, i.e., they are re- 

 gurgitated in the balls of castings, mostly in the evening after the birds have gone to rest; 

 the rest pass through the intestines. Nussifraga usually breaks the stone before swallow- 

 ing both the seeds and the fragments of the shells. Garrulus only occasionally makes castings 

 and is of less importance in endozoic distribution. Both of these are important, however, 

 in the distribution of larger nuts, as those of the oak, beech, hazel, walnut, chestnut, and pifion, 

 which they bury like squirrels for winter food. The species of Corvidae also eat excrements 

 of mammals, and are themselves eaten by owls, hawks, martens, etc., and thus constitute 

 links in chains of dispersal, whereby seeds are carried long distances. They also eat young 

 birds and rodents, and carrion, and disperse seeds in the same way as the birds of prey. Most 

 of them are more or less migratory and therefore often carry the seeds long distances. The 

 author enumerates 151 species of plants which he has found distributed by different species 

 of Corvidae. The list of reference literature numbers 139 titles. — P. A. Rydberg. 



231. Hexdricksox, A. H. The common honey bee as an agent in prune pollination. Cal- 

 ifornia Agric. Exp. Sta. Bull. 291 : 215-236. IS fig. Jan., 1918.— See Bot. Absts. 2, Entry 726. 



232. Hesselman, Henrik. Iakttagelser over Skogstradspollens Spridningsformaga. 

 [Dissemination of pollen from forest trees.] Meddel. Statens Skogsforsoksanst. 16: 27-60. 

 Fig. 1-3. 1919. — The author studied the pollen dissemination of forest trees by placing petri 



