MULTIPLICATION OF (T.LI.S 



237 



388. Bordered i>it~ in 

 pine wood. 



the walls of cells take on certain definite markings. Some 

 of the names applied to these markings arc- 

 Pitted, with little holes <r depressions, forming very 

 thin places, as seen in seeds of sun- 

 flower, and in the large vessels in 

 the stem of the cucumber. 

 Bordered pits, when the pits are in- 

 closed in the cell-wall, as in wood of 

 pines and other conifers. Fi<^. .*{SS. 

 Spiral, with the thickening in a spiral 



band, as in the primary wood <>t' most woody plants 

 and in the veins of leaves. Fig. 389. 

 Annular, with thickening in the form of rings; seen 

 iu the large vessels of the bnndles in stem of Indian 

 corn. Fig. 389. 

 Scalariform, with elongated thin places in the wall, 

 alternating with the thick ridges which appear like 

 the rounds of a ladder. Fig. 389. Tb.ese are well 

 shown in a longitudinal Bection >f the root of the 

 brake fern (Pteris). 



391. MULTIPLICATION OF CELLS. Cells give rise to 



new cells. Tims does the plant grow. The most com- 

 mon method by which cells are multiplied is thai called 



cell division. A modified form of cell 

 division is called budding. Cell di- 

 vision is a process by which two 

 (or more) cells are made from one- 

 original cell. dlls which havt on 

 Him mlii hi i a! protoplasm tin usually 



hi"*/ in /in in iiil division. The 

 pri icess is at fivsl an \nU rnal o 



in. 



The nucleus gradually divides int< two inn and 



the protoplasm of the cell is apportioned between 

 these two nuclei; a new cell -membrane, or partition 

 wall, is usually thrown across and tl II is complete!} 



