436 ELEMENTARY BIOLOGY. [CHAP, 



in the water; and that, except so far as the reproductive 

 organs are concerned, there is a morphological differentia- 

 tion of organs, unaccompanied by a corresponding phy- 

 siological differentiation. 



Nitella is a rarer plant than Chara, and is simpler in 

 structure, its axis being devoid of the cortical layer. In 

 other respects, however, it is very similar to Chara, and its 

 structure is more easily made out. * 



[The Characea, or plants belonging to the genera Chara and 

 Nitella, are found in all parts of the world, and belong to the 

 class of Alga, which also includes the sea-weeds.] 



LABORATORY WORK. 



A. Naked-eye characters. 



Note the slender elongated axis {stem); the whorled 

 appendages (leaves); the nodes and inter nodes; the shortening 

 of the latter towards the apex of the stem; the rhizoids. 



a. The roots ; small; serving chiefly for attachment, 

 the plant getting most of its nutrition, through 

 other parts, from matters dissolved in the water. 



b. The leaves ; their sub-divisions (leaflets) ; their 

 form, size, &c. 



c. The oogonia and antheridia ; their position, 

 size, form, colour. 



Draw a portion including two or three internodes. 



B. Histological structure. 

 a. The stem. 



i. Examine the outside of a fresh internode with a low 

 power, or pocket lens, to see the spirally-arranged 

 cortical cells. 



