FEESHWATER ALGiE. 113 



FEESHWATEE ALG^.* 



BY A. W. WILLS, F.C.S. 



The objects of the " Midland Naturahst " are, like those of the 

 several societies in the Union which it represents, at least threefold, 

 viz. : — 1st, to record such original researches and observations as there 

 members may be fortunate enough to make ; 2nd, to facihtate a complete 

 record of the flora and fauna of the several districts of the Midland 

 Counties ; and lastly, to enable lovers of Natural Histoiy to hold out a 

 helping hand to one another by pointing out how others may pursue 

 most profitably such branches of study as they have themselves specially 

 affected, and by communicating to one another such hints as are derived 

 from their individual experience, whereby success may be ensured, time 

 saved, or gaps in special lines of investigation filled up. 



The present paper falls within the scope of the last division ; it 

 records little or nothing which is original ; its object is to invite attention 

 to a branch of microscopical study in which there is ample scope for 

 observation, and to point out in what fashion the examination of the 

 great gi'oup of plants known as the Freshwater Algso may be successfully 

 begun and carried on. 



In doing this it vrill be convenient to ask and briefly to answer the 

 following questions : — "What are Freshwater Algae, and why will they repay 

 patient investigation ? Wliere must they be sought ? What are the 

 general features of their structure, modes of reproduction and mor- 

 phology, and the characteristics of the principal gi'oups into which they 

 are divided ? How are they best collected and preserved ? And how 

 should observations be recorded ? 



1st. — Freshwater Algse are minute plants, mostly requiring con- 

 siderable magnifying power to reveal their structm-e, belonging to that 

 great group of water-weeds included in the somewhat loose tei-m of 

 Confervoidece or Chlorospermeas, of which the coarser green weeds of the 

 sea shore are the most f amihar examples. 



The imperfection of a classification by reference to the colour of 

 these plants or of their spores will become evident from the outset ; it 

 must be accepted only as a rough division by which the majority only of 

 the genera are covered. 



The freshwater species are far more delicate in texture and various 

 in form than the marine ones, and comprise, in addition to those larger 



* Description of Figubes. — Plate I. 

 Tig. l.—Cldorococcum vulgare, from, the ha,ik of an ash tree, showing subdivision 



of cells into groups of two, four, &c. 

 Fig. 2.— ProtococcMS.— Species allied to P. pluvialis, from a freshwater aauarium, 



showing subdivision of cells and formation of motile forms. 

 Fig. 3.— CTrococcus sp ? Hass., from damp wall of a greenhouse. 

 Fig. A.—Frotococcus sp?, from wet rocks at Church Stretton. 

 Fig. S.—Tetraspora lubrica, from bogs in Sutton Park. 

 Fig. 6.—Micra8terias rotata and Cosmarium coclatum, from bogs in Sutton Park, 



showing increase by cell-division. 



N 



