BLACK: INFLORESCENCE AND FRUIT OF PYRUS MALUS 537 



the entire torus and carpels conjointly; in the latter, such growth 

 is intercalary; the carpels and that part of the torus which bears 

 the sepals, petals, and stamens, maintain an independent growth." 

 A conclusion substantially similar to that of Kraus has been 

 reached by the writer with the exception of the interpretation of 

 the term intercalary. 



Jost (41) defines intercalary growth as the interpolation of a 

 new region between two zones which are already fully developed, 

 giving as an example, Oedogonium. Sachs (42) cites the growth 

 at the base of the internodes of grasses, the production of new 

 laminae in Laminaria and the development of the inflorescence 

 in the fig as examples of intercalary growth. 



In discussing terminal and intercalary growth, Van Tieghem^ 

 states that if growth is exclusively terminal, the parts of the 

 structure are superposed gradually from base to summit according 

 to age. The formation is thus basifugal. When growth is exclu- 

 sively intercalary it may occur equally in all parts of the structure 

 at the same time or it may be localized in a certain transverse 

 zone. In the first place all parts are of the same age, their forma- 

 tion is simultaneous. In the second case the parts are of different 

 ages and successive. Depending on the position of the interca- 

 lary growth, we may have: growth towards the apex, or basifugal 

 growth; growth towards the base, or basipetal growth; or, growth 

 may be intermediate, when it is said to be mixed. Finally if both 

 terminal and intercalary growth occur at the same time, which is 

 very frequent, the two results are superposed. The apex produces 

 the parts at first in basifugal order, then, in these parts are inter- 

 calated the new ones which have formed following the simultane- 

 ous method or one of the other three. 



Different zones of growth may be distinguished in very simple 

 plants according to Pfeffer- (43), who states that "not only apical 

 and intercalary vegetative zones, but also zones in which only 

 growth in length is active, may be present in trichomes, and 

 also in the filaments of algae and fungi. Moreover, the remark- 

 able forms assumed by unicellular diatoms and desmids suffice 

 to indicate that localized differences in growth are possible even 

 in cells which retain their embryonic character." 



1 Page 34. 

 ^ Page lo. 



