330 SUMMARY OF CURRENT RESEARCHES RELATING TO 



and form in the interior ramifications of very slender filaments. The- 

 same type is found in the larger number of Monocotyledons. In 

 Dicotyledons it occurs in Stachys, Teucrium, Bellis permim, Orohus 

 tuberosus, Frayaria resect, etc. 



The second series is typified by Paris qaadri folia. The mycelium is. 

 constantly intracellular, infection being limited to the four outer layers, 

 of cells. Much-branched hyphae forming tufts are constantly present. 

 Colchicam autumnale, several Eanunculaceas and Yiolacere, etc., belong 

 to the Paris series. In the Hepatics, which form a third series, he finds, 

 that the fungus is intra-cellular, and inhabits the thallus, which spreads 

 over the surface of the soil ; tufts and sporangioles are formed by the 

 mycelium. The OrchideEe present yet another type ; the intra-cellular 

 hyphre form compact coils, which remain intact (Pilzwirthzellen), or 

 become digested by the host (Verdauungzellen). The author finds a 

 somewhat similar condition of growth in the roots of Tamus communis 

 and Psilotum triquetrum. 



It has been impossible, in the absence of fructification, to identify 

 any of the fungi. In each series, which embraces a varied collection of' 

 host plants, the fungus is throughout of the same nature. And 

 probably it will be found that there are only a few species that form 

 Mycorhiza. 



Hemicellulose as a Reserve Substance in European Forest- Trees.* 

 — H. C. Schellenberg points out that the mucilaginous, or cellulose,, 

 layers described in the interior of the bast fibres in various trees during 

 the period of winter rest is really hemicellulose, and is to be regarded as. 

 a carbohydrate reserve, which disappears in the spring. The author has. 

 demonstrated the existence of similar reserves of hemicellulose elsewhere., 

 as in the parenchyma of the cortex and in the collenchyma. 



Heterorhizy in Dicotyledons.! — A. Tschirch finds that the roots of 

 many dicotyledonous plants show a differentiation into nutritive and 

 attaching. The attaching roots, those that is, which serve to fasten the 

 plant in the soil, are characterised by the presence of mechanical tissue,. 

 by the absence of pith, and by their larger stele. 



Irritability. 



Geotropic Response in Stems4 — Julia A. Haynes conducted a. 

 series of experiments with a view to determine the angle of deviation 

 from the normal vertical position at which stems show the strongest , 

 geotropic response. Unbranched stems and actively growing young 

 plants formed the subject of experiment. Two methods were used — 

 that of " alternating stimulation " and the "after-effect" method. In 

 the former, by means of a special frame devised for the purpose, plants 

 were set first at an angle of 1)0° on one side of the vertical, and then at. 

 an angle of 135° on the other side, or vice versa. Of the 395 plants, 

 used, 53 did not respond in the time given to the experiment. Of the- 



* Ber. Deutsch. Bot. Gesell., xxiii. (1905) pp. 36-45. 



t Flora, xciv. (1905) pp. 68-78. 



X Amer. Nat, xxxix. (1905) pp. 77-85 (1 fig.). 



