CIRCULATION AND FORMATION OF WOOD IN PLANTS. 597 



Fig. 8. A less-developed absorbent, showing its approximate 

 connexion with a duct. In their simplest forms, these structures 

 consist of only two fenestrated cells, with their ends bent round 

 so as to meet. Such types occur in the central mass of the Turnip, 



where the vascular system is relatively imperfect. Besides the 

 comparatively regular forms of these absorbents, there are forms 

 composed of amorphous masses of fenestrated cells. It should 

 be added that both the regular and irregular kinds are very vari- 

 able in their numbers : in some turnips they are abundant, and in 

 others scarcely to be found. Possibly their presence depends on 



