272 SUMMARY OF CURRENT RESEARCHES RELATING TO 



frequently entirely disappeared in older tubercles. The author finds 

 them also almost universally diffused among Papilionaceae, as well as 

 many Caesalpinieae and Mimoseas, from all climates and soils, but 

 exhibiting very different forms in different species. He regards them 

 as probably the means through which the food-material obtained from 

 the soil is assimilated. 



Tubercles on the Roots of the Alder.* — Herr J. Brunchorst 

 has re-investigated the cause of these structures, and pronounces 

 decidedly against Holler's view that they are caused by the Plas- 

 modium of a Plasmodiophora. Since, however, the germination of 

 the spores has not yet been determined, it is impossible at present to 

 decide the systematic position of the fungus to which they belong. 



The tubers on the roots of Elseagnacese correspond altogether in 

 structure to those of A Inus. 



Cell-markings as Specific Characters of Exogenous Trees.f— 

 Examining sections of a very large number of American exogenous 

 woods, Mr. P. E. Lawrence and Mr. C. S. Eaddin have come to the 

 conclusion that the markings on the cell-walls are quite unreliable as 

 characters for the distinction of species and even of genera. The 

 same species may differ in this respect according to the soil in which 

 it grows, while species of the same genus showed no relationship to 

 one another ; and the markings of trees belonging to widely separated 

 natural families presented cell-markings almost indistinguishable 

 from one another. 



Biology of Water-plants-l — Herr H. Schenck contributes an 

 exhaustive account of the anatomy and physiology of these plants, 

 which (excluding seaweeds) he classifies under three heads : — those 

 which are altogether hydrophytes; those which have the capacity, 

 under special circumstances, to live on the land in peculiar forms ; 

 and those which are truly amphibious. 



Water-plants are as a rule characterized by the leaves being 

 deeply cut, to enable them to withstand the currents of water and to 

 be reached by the diffused light. Exceptions are furnished by the 

 broad-leaved Potamogetons. The stem is usually thin and flexible, 

 and provided with stolons, and there is no difference in the structure 

 of the primary and secondary axes. The roots are reduced, and serve 

 rather as organs of attachment than of absorption, and are often 

 destitute of root-hairs. The stem is endowed with rapid apical 

 growth, and has no secondary increase in thickness. For the purpose 

 of fertilization the flowers are sometimes elevated above the surface 

 of the water and conspicuous, when they are fertilized by flying 

 insects, or elevated and inconspicuous, when they are fertilized by the 

 wind or by insects which run on the surface of the water. Other 

 species have special contrivances for fertilization out of the water, 



* Versamml. Deutsch. Naturf. Strassburg, 1885. See Bot. Centralbl., xxiv. 

 (1885) p. 222. 



t The Microscope, v. (1885) pp. 241-3. 



j Schenck, H., ' Die Biologie der Wassergewachse,' Bonn, 1886 (2 pis.). See 

 Bot. Centralbl., xxiv. (1885) p. 355. 



