Tricotyiy and the Arrangement of Leaves. 369 



Tricotylous s|)cciincns of species willi ;i decussate 

 arrangement of their leaxes very often produce tlie lower 

 leaves of the stem in whorls of three. Sometimes this 

 extends all the way up, or at least to the inflorescence, 



Fig. 74. Dracocephahim moldaviciun. Twisting of the 

 main stem as the result of a breeding experiment ex- 

 tending over four years. (Compare below Fig. 82.) 



sometimes, however, it reverts to the decussate arrancre- 

 ment sooner or later as we proceed ui)wards. Very often 

 also the latter follows immediately on the seed-leaves 

 (Fig. 76 B). All such cases can often be observed in 



