20 



BOTANY. 



first observe certain things about the plant enumerated in paragraphs 41 and 42, 

 - so that they will be able to tell it from other minute green 

 algae. When these things have been observed the protoplasm 

 can be demonstrated. At one sitting each pupil can ob- 

 serve the things called for in paragraphs 41-44 ; make 

 sketches and notes. 



41. Chlorophyll bands in spirogyra. We first 

 observe the presence of bands, green in color, 

 the edges of which are usually very irregularly 

 notched. These bands course along in a spiral 

 manner near the surface of the thread. There 

 may be one or several of these spirals, according 

 to the species which we happen to select for 

 study. This green coloring matter of the band 

 is chlorophyll, and this substance, which also oc- 

 curs in the higher green plants, will be considered 

 in a later chapter. At quite regular intervals in 

 the chlorophyll band are small starch grains, 

 grouped in a rounded mass. 



42. The spirogyra thread consists of cylind- 

 rical cells end to end. Another thing which 

 attracts our attention, as we examine a thread 

 of spirogyra under the microscope, is that the 

 thread is made up of cylindrical segments or 

 compartments placed end to end. We can see 

 a distinct separating line between the ends. 

 Each one of these segments or compartments 

 of the thread is a cell, and the boundary wall is 

 in the form of a cylinder with closed ends. 



43. Protoplasm. Having distinguished these 

 Fig. s. parts of the plant we can look for the proto- 



Thread of spiro- , .... T 



gyra, showing long plasm, it occurs within the cells. It is color- 

 ceils, chlorophyll ./.,.. 



band, nucleus, less (i.e., hvalme) and consequently requires 



strands of proto- 

 plasm, and the close observation. Near the centre of the cell 



granular wall layer 



of protoplasm. can be seen a rather dense granular body ot an 

 elliptical or irregular form, with its long diameter transverse to 



