THE ANGIOSPERMAE : STEMS 855 



into cambium, known as the interfascicular cambium. Even where 

 parenchymatous rays have been formed they may later be bridged by a cambial 

 band, Hnking together the bundle cambia, which is formed by regression 

 {i.e., de-differentiation) of parenchyma cells. The first type of interfascicular 

 cambium, that which arises directly from the meristem ring, may form inter- 

 fascicular zones of xylem and phloem, connecting together the vascular tissues 

 of the bundles. On the other hand, the second type of interfascicular 



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pi. 



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Fig. 842. — Solarium crispiim. Longitudinal section 

 of the stem apex showing the development of 

 procambial strands in connection with the leaf 

 rudiments. 



cambium, which arises from parenchyma may, and usually does, form nothing 

 but more parenchyma, continuing outwards the primary medullary rays, 

 so that the bundles remain permanently isolated. The former condition is 

 characteristic of the truly woody trees and shrubs, the latter condition includes 

 many woody climbers, such as the Vine. 



The true herbaceous plant has no interfascicular cambium, and in the 

 most reduced cases no cambium at all, the bundles being formed entirely 

 from procambium, which originates in separate strands directly from the 

 apical meristem, without even the formation of a meristem ring. 



The scheme on page 856 summarizes these complicated relationships. 



