ONTOGENESIS 



137 



animal types that have a plantlike habit, such as 

 the sponges, ccelenterates, and tunicates. Familiar 

 examples are the " runners " of strawberries, the 

 " shoots " of willows and other trees, the tubers 



FIG. 51. Habit of growth of a grass: A, aerial stem terminating in 

 a branched inflorescence; B, underground stem or rhizome sending up a 

 new shoot from one of the nodes; C, section through the node of a stem 

 that has been placed horizontal, showing the sheathing leaf base, I, and 

 the beginning of the upward curvature of the stem. (From Curtis.) 



of potatoes, etc. The most primitive condition in 

 plants was doubtless that of a plant-body (thallus), 

 dying or drying up in the middle, and leaving two 



