Tricot yly and the Arrangement of Leaves. 369 
Tricotylous specimens of species with a decussate 
arrangement of their leaves very often produce the lower 
leaves of the stem in whorls of three. Sometimes this 
extends all the way up, or at least to the inflorescence, 
Fig. 74. Dracocephalwn moldavicum. 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 arrange- 
ment sooner or later as we proceed upwards. Very often 
also the latter follows immediately on the seed-leaves 
(Fig. 76 B). All such cases can often be observed in 
