1909] LEAVITT—HOMOEOSIS IN PLANTS 



DO 



the sense in which they are presented, it is indisputable that stages 

 of development supposed to be concatennated in a fixed order are 

 subject to the most violent dislocation-that a stage belonging to one 

 morphological category may pass into another of a different category. 

 Abnormalities which are traceable to very ordinary features of 



may 



moment 



may ever have been thought to possess. Historical significance can 

 be restored to them only by application of the laws (if we may so 

 speak of the operations) of homoeosis. If homoeosis much more 



under 



homology 



very special conditions, then frequent homoeotic metamor- 

 phosis of a particular organ in a particular direction may be thought 

 to be indicative of the derivation of the organ. But I think that the 

 aamission of homoeosis in any case is practically fatal. The method 

 ta J" re ^ Cethen becom es too roundabout to be acceptable to modern 



formations agree 



morphology, of anatomy 



** add only a reflected light to the general illumination. 



over^h ntmg theSC W ° rdS I haVe in mind P arti cularly the W 5 u C u ai c 

 conifo m0rphol °S ical na *ure, or origin, of the ovuliferous scale in 



m 



Perhaps no 



rphologists 



ter for d' • ailUiUCU mux pnuiogisis more mat- 



own hv ' SpUtatlon than thi * scale, which has a vast literature of its 

 T»n. I! T St eminent authorities-LiNNAEus, A. Braun. Schlei- 



DEN VOW AT «**«» ^iiNHA^US, fS.. JDKAUJN, OC 



Wj " 10HL > Ei chler, Sachs, Baillon, Strasburger, 



VAN 



Masters, Noll 



others Th h • ' lv±ASTER s, JNoll, Uelakovsky, and 



u Pon everv ^ Tks ° f these auth <>rs have been various, and based 

 TeratoW f° nCeiVable consideration, not least upon abnormalities, 

 ^e as su appealed vei 7 differently to different students-to 

 theory; t0 PP ° rtln S one doctrine, to others as favoring a different 



hav W no «*v*fl aS ° f gr6at ° r even decisive weight, to others as 



ciallv „n P ersistentl y, has relied 



studied 



ciall y upon u h T Up0n abnormali ties, and espe- 



betu 'een the tertil ^'^ ° f intermediate formations, such as those 



ance of a shoT^ C SCale aS ** seDarates int0 P art s (at the appear- 



o ) and the leaves (or bud scales) of the shoot. This 



