48 Plant Tissue Culture 



while the epicotyl and plumule tend to form roots 

 and develop into normal plants without serious 

 difficulty. Thus, even in the embryo there is the 

 beginning of an apparent loss of totipotency, a 

 segregation of function which is marked in the 

 root, somewhat less in hypocotyl and cotyledon, 

 and lacking in epicotyl and plumule. 



As the embryo grows into a plant, there is a pro- 

 gressive maturation of some tissues so that, ex- 

 cept for "juvenile" cells like the medullary ray 

 parenchyma scattered through the plant body, 

 there are segregated certain meristematic re- 

 gions which carry on the function of prolifera- 

 tive growth (Priestley, 1928, 314; Priestley and 

 Swingle, 1929, 316 ; Jaeger, 1928, 298) . These re- 

 gions are: the terminal growing points of roots 

 and stems, the lateral meristems designated as 

 cambiums and phellogens, and intercalary meri- 

 stems in the procambial region, at the base of the 

 internodes in grasses and lianes and at the base 

 of some leaves or, as in Camptosorus, near the 

 tips of leaves. 



The intercalary meristems require considerable 

 manipulation for their excision and therefore suf- 

 fer rather severe injury. Scheitterer (1931, 109) 

 had slight success with the intercalary meristem 

 of grasses, and none of those of lianes have been 

 cultivated although they should be fairly easy to 



