1909] LEAVITT—HOMOEOSIS IN PLANTS 45 



ovate crispate petals. The two lateral sepals, however, differed from 

 the dorsal in that the inner half of each became colored like the 

 labellum. The latter organ forms in this species, by the inflection of 

 its margins, a loose tube, embracing the column, open distally and 

 expanding to form the landing-stage for the pollinating insect. The 

 floor of the tube has a broad yellow stripe, widening toward the 

 mouth, and at the extremity replaced by a large purple or crimson- 

 magenta patch. These colors are bounded by the pale magenta 

 body-color of the flower. In the abnormal specimens the halves of 

 the lateral sepals next the labellum reproduced the color-pattern of 

 half the labellum. The halves away from the labellum were like 

 the rest of the flower in hue. This peculiar distribution of the colors 

 becomes interesting when an examination of the base of the perianth 

 shows that in Cattleya labiata the foot of each lateral sepal is close to 

 the foot of the labellum and overlaps it by just half— the half corre- 

 sponding to the homoeotized half-limb in the abnormal flowers; 

 while the other perianth segments stand somewhat apart from the 

 lip- In these particolored sepals the discrimination between homoe- 

 otic and non-homoeotic areas seems to be directly related with con- 

 tiguity to the "source" of the derived features. 



Penzig 33 has dwelt upon this phase of the phenomenon which we 

 are now calling homoeosis, in his general considerations of the sig- 

 nificance of monstrosities and in his arguments for the theory of 

 Delpino regarding the nature of the fertile scale in Abietineae. He 

 was impressed, as everyone must be, with the agreement between 

 the facts of this category and the formative-stuff theory of Sachs. 



10. A compound member may be changed in such a way that some 

 or all of the parts exhibit the plan originally characteristic of the whole 

 mmber {entropic homoeosis). 



The general plan of organization is transferred from the member 

 as a whole to the constituent parts. Compound members may thus, 

 y an entropism of form, suddenly become decompound. This form 

 p. homoe °sis has already been illustrated in the description of the 

 lerson fern above. Further examples in leaves of ferns and flower- 

 ln g plants may be noticed here, since this variation has an interesting 

 Fe atlon t0 the question of the evolutionary origin of compounding; 



33 p flanzen-Teratologie, /. c. (and elsewhere). 



