54 



GENERAL DIFFERENTIATION OF THE PLANT-BODY 



a purely comparative meaning, that is to say, it is merely another way 

 of stating the fact that the cells in the first plant have not coalesced 

 with one another ; and it is only of significance if it gives probability to 



the congenitally concrescent body having had its 

 phylogenetic origin in the free hairs. A support 

 to this declaration would be obtained if a plant 

 were known in which the hairs occurred as is 

 shown at /// in the figure, where they are only 

 combined in their lower part, that which is shaded 

 in the diagram. Such a condition might be reached 

 in two ways either the hairs might grow out at 

 first free and then be raised up by elongation of 

 their common basal part, or at the outset a cell-mass 

 might arise, like that at 7F, corresponding with the 

 shaded part of ///, and upon its top the three free 

 cells might then shoot out. We find in the origin 

 of the gamopetalous corolla examples of both 

 these methods. 



A phenomenon which corresponds exactly with 

 the concrescence of hairs as just described is observ- 

 able in the hair-roots of many Florideae and of 

 some liverworts. In most species of these groups 

 solitary hair-roots are known ; in some of them 

 cell-masses occur which may be designated ' con- 

 genitally concrescent ' root-hair tufts ; such are 

 found in Polyzonia jungermannioides among the 

 Florideae l . 



In all cases where a congenital concrescence is 

 assumed upon comparative grounds historical de- 

 velopmental proof must show hoiv it really takes 

 place. Both methods of investigation must mutually 

 complete and correct one another. The inferior 

 ovary, for example, was from the historical develop- 

 mental side very often considered as formed of the 

 cup-like torus ; the carpels would then be repre- 

 sented by the styles only. Comparative study 

 however led to the conclusion that in the inferior 

 ovaries the carpels take a share in the formation 

 of the ovary, and that from them the ovules arise ; 



and this without giving thereby a clear explanation of the process itself. 

 The accurate pursuit of the history of development has shown, in all cases 



FIG. 23. Spathiphyllum platy- 

 spatha. The unilateral inflores- 

 cence viewed from above some- 

 what obliquely. The spadix is 

 ' concrescent ' with the spathe ; 

 there are two rows of staminate 

 flowers, and between them the 

 pistillate flowers. 



With regard to the liverworts, see my ' Pflanzenbiologische Schilderungen,' i. p. 161, fig. 66. 



