20 



BOTANY. 



■organism ; it absorbs nourishment, assimilates, grows, and 

 rejDroduces 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 iu dividual 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, 

 ^u^* ■?,■"■* •^™l'i?''"^®"t and structural characters of the plant 



the epidermis of the petal . ^ nf i 



of a pansy ( woia i!«c<j«(w), and all its parts. It is thus the Morpno- 



showliig prolongations ot , . , _- t, . ,, _ , 

 the free (upper) sides of the logical Unit 01 the plant. 



ehartie. ^^' ~ *' "' 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- 



Fio. 96. 



Fis. 9. 



Fi?. 9. — ^A crosB-Bsction through the petiole of Nwphav advma ; s, a, star-shaped 

 cells projecting into the intercellular spaces i,i;g,a reduced flbro-vascnlar bundle. 

 Magnified. — ^Arter Sachs. 



Fig. 94. — Stellate cells from the pith ot Juneus ^ustis, magnified.— After Du- 

 chartre. 



ant of the physiological activities of its individual cells. 

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



