3.] 



CHAPTER I. GENERAL MORPHOLOGY. 



17 



near together, but as growth proceeds they become more and 

 mere widely separated by the increase in the adult portion of the 

 body. In a few cases (e.g. Spirogyra, and some other filamentous 

 Algae) all the cells remain embryonic, the growth in length of the 

 filament being effected by the transverse division of the cells and 

 the subsequent elongation of the new cells formed. 



The primary function of the growing-point is to increase the 

 size, more especially the length, of the member to which it be- 

 longs ; but where the body is segmented, the growing-points are 

 also the seat of development of the secondary members. 



The embryonic regions of the body are termed " growing-points " 

 because they are most commonly situated at the apex of the mem- 

 bers. Thus, in a cormophytic embryo, there is a grow ing- point at 

 the apex of the primary stem, and one at the apex of the primary 



B. 



FIG. 7. Growing-points showing development of secondary members. A, apical grow- 

 ing point, with apical cell, of Stypocaulon scoparium (x30). JB, intercalary growing-point 

 (where the transverse lines are close together) of Desmarestia ligulata in longitudinal 

 section (x60). C, apical growing-point, with apical cell, of Choetopteris plumosa (x40), 

 (after Falkenberg). 



root. But this is not necessarily the case. The growing-point 

 may be situated between the base and the apex, as in some Algce 

 (e.g. Ectocarpus and Laminaria), and in leaves (e.g. Grasses, 

 Onion, Iris, etc.), when it is termed an intercalary growing-point. 

 In some cases both an apical and one or more intercalary grow- 

 ing-points co-exist, as in the stem of Hippuris, Myriophyllum, etc. 



One of the most remarkable instances of an intercalary grow- 

 ing-point is that occurring in connection with the development 

 of hollow, more or less tubular structures (e.g. inferior ovaries, 

 "calyx-tube " of Rosaceoe, gamopetalous corollas, inflorescence of 

 the Fig, pitchered leaves of Nepenthes, Utricularia, etc.). Taking 



v. s. B. C 



