REPRODUCTION AND DISPERSAL 



893 



if an inflorescence is cut off and allowed to strike root in a moist chamber 

 the tip grows into a vegetative shoot (figs. 1199, 1200). The oldest 

 buds develop into the usual 

 flowers, while younger buds de- 

 velop into cleistogamous flowers 

 without prominent corollas; still 

 younger buds develop only the 

 calyx, and the very youngest 

 lateral buds, as well as the ter- 

 minal bud, develop vegetative 

 shoots. If a flowering shoot of 

 Myriophyllum helerophyllum is 

 transferred from a pond to a 

 covered aquarium, it becomes 

 transformed into a vegetative 

 shoot. Ajuga reptans has three 

 phases, a rosette, a flowering 

 shoot, and a stolon, and any of 

 the three can be induced at any 

 time by supplying the requisite ex- 

 ternal conditions. If the flowers 

 of Opuntia are removed from the FlGS I lg9 ^ 200> _ variation in the flower- 



plant and placed in the soil, they ing shoots of Veronica Chamaedrys: 1199, an 



soon strike root and give rise to ordinar y flowering shoot with buds, flowers, 



and young fruits; 1200, a similar shoot that 

 was placed in moist air at the inception of 

 anthesis ; note the metamorphosis of the upper 

 part into a leafy shoot. From KLEBS. 



which also has three phases, comparable to those of Ajuga; vegetative 

 activity may be made to continue indefinitely, stolon formation may be 

 eliminated, and phenomena unusual in nature (such as rosette for- 

 mation at the stem apex, and the transformation of the inflorescence 

 into a vegetative shoot) may be induced at will. 



Reversibility of stages is not confined to the seed plants; if a fruiting shoot of 

 Selaginella lepidophylla is cut off and placed in the soil of a moist hothouse, it be- 

 comes transformed into a vegetative shoot, even developing rhizophores. Reversi- 

 bility can be induced also in animals, for if a polyp of the hydroid. Campanularia, 

 is brought into contact with a solid body, it gradually becomes undifferentiated and 

 finally develops into a stolon, whereas removal to the original habitat soon results in 

 a transformation back to a polyp. It may be noted finally that reversibility is the 

 usual thing in the pineapple, a vegetative shoot developing at the apex of the fruit. 



f199 



1200 



vegetative shoots. Most striking 

 of all, perhaps, are the reactions 

 of the xerophyte, Sempervivum, 



