PART II. 



MORPHOLOGY AND LIFE HISTORY OF REPRE- 

 SENTATIVE PLANTS. 



CHAPTER XIV. 



SPIROGYRA. 



283. In our study of p-rotoplasm and some of the processes of 

 plant life we became acquainted with the general appearance of 

 the plant spirogyra. It is now a familiar object to us. And in 

 taking up the study of representative jjlants of tlie different 

 groups, we shall find that in knowing some of these lower plants 

 the difficulties of understanding methods of reproduction and 

 relationship are not so great as they would be if we were entire- 

 ly ignorant of any members of the lower groups. 



284. Form of spirogyra. — We have found that the jilant 

 spirogyra consists of simple threads, with cylindrical cells 

 attached end to end. We have also noted that each cell of the 

 thread is exactly alike, with the exception of certain ' ' hold- 

 fasts " on some of the species. If we should examine threads in 

 different stages of growth we should find that each cell is cajjable 

 of growth and division, just as it is capable of performing all the 

 functions of nutrition and assimilation. The cells of spirogyra 

 then nuilti])ly by division. Not simply tlie cells at the ends of 

 the tlu'eads but any and all of the cells divide as the)' grow, and 

 in this way the tlireads increase in length. 



285. Multiplication of the threads.- In sUulviiig living material erf this 

 plant \vr liiLVi' proliaMy iiotrd that tin- tlirt.uls oltcn ln-i < nur l>rii1-.cii 1 >}■ Iw" of 

 the adjacent cells (.if a thread bttccming separated, "this may be and is aecom- 



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