THE STEM OR SHOOT. 



101 



vegetative stem and a basal rosette of leaves, the 

 former may develop its internodes and grow into an 

 elongated leafy axis, as in the daisy (Bell is perennis) 

 forming the variety sometimes known as B. hybrida. 



The same is true of other rosette-forming plants, 

 e.g. Carduus (Cnicus) acaulis : in this case the 

 " flowers," normally sessile in the midst of the rosette, 

 become seated on an elongated shoot. 



The tendril of the Ampelidacese in the normally- 

 growing plant arises laterally, on the stem on the side 

 opposed to the leaf -insertion, and apparently affords a 

 case of an extra-axillary branch ; morphologically, 

 however, the whole shoot is constructed sympodially 

 and the tendril really represents a modified inflores- 

 cence-axis which has become displaced from its original 

 terminal position on the axis by the relatively much 

 stronger development of the axillary shoot at its base. 

 As the plant grows the same thing happens congeni- 

 tally each time a tendril is formed, so that the main 

 axis of the plant consists of a concatenation of axil- 

 lary shoots. Now, abnormal cases occur from time 

 to time in which the relative strength of development 

 as between tendril and axillary branch, as we usually 

 see it, becomes reversed, and the tendril grows out 

 into a vigorous terminal leafy shoot or inflorescence 

 while the axillary shoot becomes much more weakly 

 developed and relegated to a lateral position. This is 

 an excellent instance of reversion to an ancestral con- 

 dition. Cases of this kind have been observed both 

 in the vine (Vitis vinifera) and the Virginian creeper 

 (Ampelopsis hederacea). 



Bulbs occasionally proliferate. Gay describes a 

 bulb of the snowflake (Leucojum eestivum) which, owing 

 to the swelling of the internodes, produced the appear- 

 ance of two or three bulbs one above another ; Irmisch 

 observed the same phenomenon in L. vernuni (fig. 

 28), and it has been cited in the snowdrop (Galanthus 

 nivalis), and also in the onion (Allium cepa) and other 

 plants. 



