20 



BOTANT. 



organism ; it absorbs nourishment, assimilates, grows, and 

 reproduces its kind. In the higher plants, although this 

 independence is not so evident, it still 

 exists in a considerable degree. Here 

 each cell is an individual in a commu- 

 nity ; but it still has a life-history of its 

 own, a formation (genesis), growth, ma- 

 turity, and death. It is the unit in the 

 plant. Upon its changes in size, form, 

 and structure depend the volume, shape. 

 Fig. 8.-A small piece of and structural characters of the plant 



the epidermis of tbe petal ^ 



of a pansy ( Fto/a iJncoioj-), and all its parts. It is thus the Morplio- 



Bhownig prolongations of . _ . • -' 



the free (upper) sides of the ioqical Unit Ot the plant. 



cells. Mag. — After Da- __ a xi i i i r js ji 



ehartre. 22. — As the whole structure of the 



plant is an aggregation of cells, so the functions of the 

 whole, or of any part of a plant are but the sum or result- 



Fia. «t. 



Fio. 9. 



Fig. 9. --A crosB-section through the petiole of Nitphar advena ; s, fi, star-shaped 

 cells projecting into the intercelmlar spaces Li \ ff, a reduced flbro- vascular banale. 

 Magnified.— After Sachs. 



Fig. 96. — Stellate cells from the pith of Junaus effusus, magnified.— After Du- 

 chartre. 



ant of the physiological activities of its individual cells. 

 The cell is thus also the Physiological Unit of the plant. 



