RAPHANUS SATIVUS 



303 



tained that the root and hypocotyl can replace each other in con- 

 structive function, "konstruktiver Funktion." He experimented 

 with a Red Globe type, cutting away two-thirds of the hypocotyl 

 of the young seedling. The remaining portion developed roots 

 and produced a normal fleshy axis. Golinska repeated the experi- 



-ep"^^^ 



Fig. 1 51. Diagrams illustrating progressive stages in secondary and tertiary thickening 

 of fleshy axis of Raphanus. A, root before primary xylem is completely differentiated ; B, 

 same, with primary xylem strand differentiated ; C, secondary thickening and development 

 of two broad rays outside protoxylem points (two sectors of crushed primary phloem are 

 also indicated); D, secondary thickening has resulted in splitting of cortical zone in a ver- 

 tical plane at right angles to primary xylem strand and cotyledons ; E, further splitting of 

 cortex, a periderm has been formed in pericyclic zone. Secondary cambiums are shown in 

 secondary xylem parenchyma : ca, primary cambium ; ca x, secondary cambium ; co, cortex ; 

 ««, endodermis ; «/», epidermis ; wat, metaxylem; p^r, parenchyma; /if/, pericycle; /;</, peri- 

 derm; p/j I, primary phloem; />/) i, secondary phloem ; /)x, protoxylem; w, ray; xj i, sec- 

 ondary xylem. 



ments of Minin, using large elongated radishes. He made cuttings 

 at a time when the seedling had developed its cotyledons and a few 

 small foliage leaves. In most of the plants, the upper portion of 

 the hypocotyl and even the epicotyl enlarged while the lower por- 

 tion remained slender, indicating that the potentialities for second- 

 ary thickening exist throughout the axis. 



