TllAl.LDlMlVTKS; Al, (;.!•: 



227 



plex plants consist of veiT man)' crlls. It is necessary to 

 know something of tlie ordinary living plant cell before 

 the bodies of Alga? or any other plant bodies can be under- 

 stood. 



Such a cell if free is approximately spherical in ontline 

 (Fig. 204), but if pressed upon liy contiguous cells may be- 

 come variously modified in 

 form (Fig. 200). Bounding 

 it tliere is a thin, elastic 

 wall, composed of a sul)- 

 stauce called crJhflnxe. The 

 cell wall, therefore, foi'ms a 

 delicate sac, which contains 

 the liTing substance known 

 as jirofoj)Ii/s/ii. This is the 

 substance which manifests 

 life, and is the only sitb- 

 stanee in the plant which 

 is alive. It is the proto- 

 plasm which lias organized 

 the cellulose wall about it- 

 self, and which does all the 

 plant work. It is a fluid 

 sttbstance which varies much in its consistence, sometimes 

 being a thin viscous fluid, like the white of an egg, some- 

 times much more dense and compactly organized. 



The protoplasm of the cell is organized into various 

 structures which are called ori/tiits of ihe cell, each organ 

 having one or more special functions. One of the most con- 

 spicuous organs of the living cell is the single ii)irleits,a com- 

 pai-atively compact and ttsually spherical protoplasmic body, 

 and generally centrally placed within the cell (Fig. 200). 

 All about the nucleus, and filling up the general cavity 

 within the cell wall, is an organized mass of much thinner 

 protoplasm, known as ci/tiipJa^n/. The cytoplasm seems to 

 form the general background or matrix of the cell, and the 



. OOO. Ci-II? from a moss leaf, showin2 

 micleiLS iiji in which tlitre is a nucle- 

 ohis. cytoplasm iC). and chloroplasts 

 (.1).— Caldwell. 



