1880.] 



MICKOSCOPICAL JOURTnTAL. 



45 



by tetraspores ("tetra'' because 

 of their gi'ouping in fours) ; these 

 form in sub-spherical cells at the 

 ends of the filaments, or on small 

 branchlets. Referring to the figures 

 d d d d are tetrasporangia, and 

 hhh tetraspores matured in them ; 

 these tetraspores pass out, and 

 float about in the water ; here and 

 there one finds a resting place, as 

 represented at C C in the figure. 

 Each spore may be considered a 

 mother-cell. The contents of the 

 cells are first semi-transparent and 

 slightly tinted; these characters 

 soon change and the cells become 

 turbid, then finely granular and of 

 a darker purplish color ; next the 

 protoplasmic body (cell-contents) 

 breaks up into four parts, which 

 quickly contract, round themselves 

 off, and become enveloped by a 

 membrane ; J9, D, represent cells, 

 separated from G, under still higher 

 power. They remain a short time 

 encased in the mother cell ; the cell- 

 walls are gradually absorbed ; they 

 expand, aided, no doubt, by the ac- 

 tive movements of tlie young cells 

 within ; finally the walls break and 

 the young are set free {E). These 

 young, or sister-cells, with rare ex- 

 ceptions, manifest but little activity. 

 The fact that the groupings {FF) 

 increase only in a downward direc- 

 tion, proves that they are influenced 

 by gravity rather than by indepen- 

 dent movements. All the cells do 

 not divide and redivide in the same 

 manner for an indefinite period of 

 time ; some develope true plants 

 {II, H, H, and K). In this process 

 they elongate and add cell to cell 

 until the identical form is repro- 

 duced, which primarily gave rise to 

 the spherical cells or tefcrapores. 



The point which we wish to em- 

 phasize here is the cell-division and 

 multiplication. One spore divides 

 into four ; these again divide, each 

 one into four, and these multiply 



in turn in the same manner ; this 

 process goes on until millions of 

 cells are produced from a single 

 one, and in less time than the num- 

 ber could be counted singly. 



Forms like these are generally 

 termed unicellular plants ; there 

 are names for every possible va- 

 riety, but the time is at hand, when 

 they will be recognized as spores 

 only. The most recent writer. Dr. 

 Kirchner, of Siberia, expresses more 

 doubts as to the reality of these 

 forms as specific plants than pre- 

 ceeding authors, yet hesitatingly 

 adds that he " feels assured that most 

 of them do belong to the developing 

 forms of higher types of Algge, 

 nevertheless it is impossible to tell 

 from what particular plants they 

 are derived, and whether they are 

 true developing forms, or only 

 similar to them." In The Ameri- 

 can Quarterly Microscopical Jour- 

 nal, April, 1879, I drew attention 

 to some dubious forms of a similar 

 character, and in the Bulletin of 

 the Torry Botanical Clid), April, 

 1878, I made some observations on 

 Nostocs, showing them to be essen- 

 tially embryonic forms, and now, 

 here are the forms of " Pleurococ- 

 cus,^'' which belong unmistakably 

 to the life-history of Chantransia. 

 The further we advance in the 

 knowledge of how fresh-water 

 Algge grow, the more positive is the 

 evidence that most of the unicellu- 

 lar forms are of a very dubious 

 character, regarded as perfect plants . 

 Special attention should be given 

 to this part of the study of Algae. 



But why should the spore-multi- 

 plication occur? This may be a 

 difficult question to answer. Ob- 

 servation shows, that the spores do 

 multiply very rapidly ; they crowd 

 together and upon one another, 

 and most of them finally perish 

 and thus form a crust, upon which 

 the fertile plants develope. — F. W. 



