ZOOLOGY AND BOTANY, MICEOSCOPY. ETC. 845 



of the root, even tlie growing point. The structure of this latter is 

 that of a sclerotium ; it is composed of a dense mass of hyphse varying 

 in diameter from 0-0024 to 0-01 mm., usually in several layers, from 

 which other endophytic hyphaa penetrate into the root between the 

 epidermal cells, which are still slenderer than those of the envelope. 

 By this structure the formation of root-hairs by the tree is entirely 

 prevented, and it is through it alone that it is able to absorb nutri- 

 ment out of the soil. It makes its appearance first on the lateral 

 roots of very young seedlings, and is constantly being replaced by 

 fresh formations on older roots. 



Dr. Frank found this structure invariably on every root examined 

 on every tree belonging to the Cupuliferse, also occasionally on 

 Salicaceae and Coniferte, but never on woody plants belonging to other 

 natural orders, or on any herbaceous plants. It is quite independent 

 ot the nature of the soil, and its specific character has not been deter- 

 mined. He regards the phenomenon as an example of symbiosis 

 comparable in all essential points to that of lichens, the mycorhiza 

 corresponding to the fungal element in the lichen, the tree itself to 

 the algal gonidia. 



Dr. M. Woronin * confirms these statements in relation to Coniferae, 

 SalicineaB, and some other trees. He regards the phenomenon rather 

 as an instance of parasitism than of symbiosis, and thinks it probable 

 that the parasitic fungus is a Boletus. He claims the priority of this 

 observation for F. Kamienski. 



Composition and Spore-cultivation of Merulius laerymans.t — 

 Prof. Poleck has investigated the mode of operation of the mycelium 

 of this fungus, which, known as dry-rot, is so destructive to timber, 

 especially that of Conifers. The proportion of water varies from 

 48 toG8-4 per cent. The amount of ash is large, varying from 

 6*33 to 9 "66 per cent. The composition of this ash varies within 

 rather wide limits ; but there was always found a large proportion of 

 phosphates. As an average it may be stated that of the dry weight 

 about 4-9 per cent, is nitrogen, and 13 per cent, oil; there are also 

 several acids and traces of an alkaloid. The author states that the 

 action of the mycelium on the wood consists in removing its mineral 

 constituents, thus destroying its solidity, and rendering it liable to 

 the attacks of other agents. The richer the wood in phosphoric acid 

 and salts of potash, the more energetically is it liable to be attacked 

 by the fungus. When once desiccated the mycelium has no power of 

 resuscitation. Mycelial filaments have been measured from 5 to 

 G metres in length. 



Prof. Poleck has been the first to succeed in inducing the spores 

 of Merulius lacrymans to germinate on their natural substratum, and 

 Uj follow out their development, which is described in detail. 



Germination of the Spores of Merulius lacrymans. j — Prof. R. 

 Hartig has l>een able to effect this in gelatin moistened with the 



♦ Fkr. Df.utBch. Bot. Gcsell., iii. (1885) pp. 205-G. 

 t IV.t. Cf-ntralM., xxii. (1885) pp. 151-0, 182-f;, 213-7 (2 figs.). 

 X Hli. iJot. Vcr. Muuchtn, Dec, 10, 1884. Sec Bot. Ccutralbl., xxi. (1885) 

 p. 155. 



