316 BOTANY. 



parasitica, grows as a parasite on the leaves of the tea plant, the mango, 

 and other plants. Zopf, in a small pamphlet, has described and figured 

 the stages of development of Crenothrix polyspora, a species which 

 causes pollution of the water at Berlin and other places. 



The cause of the motion of Oscillaricc and Diatoms has been studied 

 by T. W. Eugelmann, who, in an article in the Botanische Zeitung, 

 states that it is owing to the presence and contraction of a thin external 

 layer of protoj^lasm. Stahl found that when desmids are exposed to 

 the light they undergo certain peculiar motions, viz, their long diame- 

 ters are in the direction of the light, the distal end of the cells being 

 attached to the substratum, and at more or less regular periods the 

 cells make a half revolution, so that what was the distal end becomes 

 the forward end. Stahl also has a paper in the Botanische Zeitung, in 

 which he shows that the genus Vaucheria has a resting condition which 

 is identical with the so-called species of Gongrosira. Reinke, in Nova 

 Acta Leop. Carol., has an illustrated paper on the Cutleriacece of the Gulr 

 of Naples, in which he claims to have seen the union of the antherozoids 

 and oogouia. In tlie proceedings of the Niederrhein. Gesellsch. Schuiitz 

 has papers on the Structure of the Cells in tSiphonocladiecc and on the 

 Formation of the Fruit in the Squamariece. 



Lichens. — In the department of lichenography very little was pub- 

 lished in the United States in the present year, the only notable work 

 being the list of lichens contributed by Professor Tuckerman to the 

 report of Professor Rothrock, which has already been mentioned. In 

 Europe, however, a number of descriptive pai^ers has been published. 

 In the Journal Liuu. Soc. is an account, by Prof. T. M. Fries, of the lich- 

 ens collected during the English Polar Expedition, 1875-'76, in which, in 

 referring to the list of lichens collected by the Hayes Arctic Expedition 

 and published in the Proc. Acad. Nat. Sci. of Philadelphia, he doubts 

 the accuracy of the determinations in the case of some of the species 

 there mentioned. The Jour. Liun. Soc. also has a paper by Crombie on 

 Australian lichens, and the same writer has a notice of new British 

 lichens in GreviUea. Leighton's Lichen-Flora of Great Britain has this 

 year passed to a third edition. Additions to the lichen-flora of Europe 

 have appeared in Flora and Hedwigia from Arnold and Nylander. The 

 last-named writer has also a curious note in Flora entitled Circa Lichenes 

 vitricolas Notula. In Cohn's Kryptogamen Flora von Schlesien, the 

 second part of which appeared in 1879, the descriptive part relating to 

 lichens was worked up by B. Stein. Inasmuch as Stein himself is a dis- 

 ciple of Korber, and not a follower of Schwendener, the general intro- 

 duction on the nature of lichens was intrusted to Schroeter, who is a 

 Sch wen denerite. 



During the year the discussion as to the nature of lichens has been 

 carried on in the different journals, epecially in Flora and Grevillea, and 

 the articles have mostly been written by botanists opposed to the Schwen- 

 dener theory. In Grevillea is a iDaper by Cooke and in the Eevue Mycol- 



