316 BOTANY. 



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

 and other plants. Zopf, in a small i^amphlet, has described and figured 

 the stages of development of Crcnothrix polyspora, a species whicl^ 

 causes pollution of the water at Berlin and other i^laces. 



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

 by T. W. Engelmann, who, in an article in the Botanische Zeituug, 

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

 layer of protoplasm. Stahl found that when desmids are exposed to 

 the light they undergo certain i)eculiar motions, viz, their long diame- 

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

 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 Botanisclie Zeituug, in 

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

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

 Acta Leoj). Carol., has an illustrated paper on the Cutleriacecc of the Gulr 

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

 and oogonia. In the proceedings of the Mederrhein. Gesellsch. Schmitz 

 has papers on the Structure o/ the Cells in Siphonocladiew and on the 

 Formation of tlie Fruit in the Squamariew. 



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 Eothrock, which has already been mentioned. In 

 Europe, however, a number of descrii)tive papers has been published. 

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

 ens collected during the Fnglish 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. Linn. Soc. also has a paper by Crombie on 

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

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

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

 have api)eared in Flora and Hedwigia from Arnold and Nylander. The 

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

 vitricolas Isotula. 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 Schweudener, the general intro- 

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

 Schwendenerite. 



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

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

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

 dener theory. In GreviUea is a pax3er by Ceoke and in the Eevue My col- 



