274 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



chief function (see Hiltner, on p. 272) is to fix atmospheric nitrogen. 

 Rctotrophic mycorhiza provide the host-plants with nitrates, which 

 the fungus obtains by breaking up nitrogenous compounds contained 

 in humus. The mycorhiza occur in forest humus and peaty soils very 

 deficient in nitrates," but rich in combined nitrogen. The fungus finds in 

 the tree-roots a convenient supply of carbohydrates, and Tubeuf believes 

 that the initiative is taken by the fungus seeking these in the roots ; the 

 tree benefits by the nitrogen supplied by the fungus, and so a symbiosis is 

 Bet up. The effect of the symbiosis is that the widely spreading normal 

 roots with root-hairs become reduced to the short knotted tufts of 

 mycorhiza; transitions from one form of root to the other are figured. 

 Mycorhiza occur in peat or forest humus, in almost pure sand, and in 

 manured farm-soils. Root-hairs are best developed in dry sands or loams, 

 and in peat which is well drained ; they are less abundant in wet soils. 

 Trees grow best where they have deep roots with root-hairs, and trees 

 artificially manured outstrip those dependent on mycorhiza for their 

 supplies. There is as yet no evidence of a specific mycorhiza-fungus ; 

 it seems that many fungi can associate themselves with roots to form 

 mycorhiza. Tubeuf also has an interesting discussion on the nutrition of 

 Mistletoe.— W. G. S. 



Nematodes in Garden Plants. By Osterwalder (Zcit. f. Planz. 



pp. 338-342, 5 figs. 1903). — Eel- worms have frequently been found in 

 indoor plants, but the author directs attention to their frequent occurrence 

 out-of-doors. The course of the attack is described and figured in Phlox 

 decussata, Cystopteris frag His, Chelone glabra, Anemone japonica, and 

 A. sylvestris. The nematode in almost every case was ApJiclenclnis 

 olesistus. The author's experience is that plants attacked need not be 

 sickly, but that contact of healthy plants with leaves infested with eel- 

 worn \b, or the presence in quantity of the latter in the soil, is sufficient. 



Tr. G. s. 



Nicotiana Hybrids. By Georges Bellair (Bev. Hort. Feb. 1, 1903 ; 



pp. 54 -55 ; four illustrations). — Interesting description of the results in 

 the second generation of crossing N. sylvestris and N. Tabacwn, white 

 flowers and pink Mowers being obtained, with great diversity of form and 

 size. Offspring of first cross were identical, a few seeds being produced : 

 these were sown with above result, neither the original parental types nor 

 that of the first cross reappearing, while all differed more or less from 

 each other, justifying Naudin's definition of a hybrid as 'a mosaic' 



C. T. D. 



Nitsche, Prof. H.: Obituary Notice. By (). Nutzlin (Nat. Zeit. 

 !«"*<l r " /J > PP- 19-59; photograph; 1903).— This well-known Pro- 

 of Forest Zoology died on November 8, 1902. His best-known 

 *orkia"The Forest Insects of Central Europe." A long list of papers 

 shows how active he was. The biography is well worthy of the attention 

 of entomologists. — W* G. S. 



Nucleus (£< . Bot. Cent. xiv. ht. 1, p. 13).— Professor V. Gregoire 

 and Dr. A. \\ v n ri i V( . a preliminary note as to their observations on 

 th€ nuclei! I of COOtfl of Ttllllum. The chromatic filaments do not seem 



