294 



MR. A. S. HOENE — A CONTRIBUTION TO 



The facts that tlie number of chromosomes may vary in mutant 



ded by 



Gates* (1907) and 



by Anna M. Lutz f (1907) for (Enothera, and that giantism 



is accompanied by increase in cell-size as first shown by Gates % {(Enothera), and latei 

 by Keeble § (Frimula), show the depth as well as breadth of the new aspect of things 

 It is hardly possible, therefore, to exclude the ovule from the possibilities of mutation 



The cha 



and grades of change from orthotropy to anatropy, the origin of the 



and double integument, and even the change from many to fev^ axial rows may yield 



We 



patient and persistent experimental endeavour 



able 



conceive the origin of mutants in floral characters. Mutants 



bearing some few and 



some many 



might arise, for example, from apocarpous forms 



carpels. These could in time produce new species. If both the floral and vege 



organization alter considerably during the continuance of mutation, forms would 



exhibiting still greater diverg 



But the advent of syncarpy and epigyny again and 



:ain in different families, and the frequent occurrence of sterilization in both Mono- 

 tyledons and Dicotyledons, culminating time after time in the evolution of uniovulate 

 aries, whilst increasing enormously the tale of floral diversity, nevertheless contribute 

 ward the evolution of synthetic and convergent structures. 



Origin 



The interpretation of phylogenies must be influenced by views of 



and the orio^in of new forms 



postulated bv the Mutation Theory, is to render the 



I 



of affinities more problematic than 



It is the custom to sort plants 



divisions and groups according to this or that bias, and to construct a phylogenetic 



branch of the great tree of descent 



but 



Mutation Theory brings home 



s that that which is actually accomplished in Systematic Eotany is the aggregation o 



nking of species, genera, and even families, as the case may be, that have attained i 



similar level in evolution, a similar resultant eff'ect of racial experiences. These aggre 



gations may or may not be 



The Compositse, for example, form a lioraog 



group consistmg of genera in the same phase of synthetic and economic development ; 

 but is it certain that the members of the family are bound by the bonds of relationship, 

 and are traceable to a single progenitor ? 



A general device in Comparative Morphology is to seek for clues to an interpretation 

 of the origin of a structure from morphological series, and thence deduce a concept of 



affinity. But spacial series may 

 exemplified by the sterilization seri 



ot 



ily coincide with series in time, as 

 the Caprifoliaceae and De Vries's CEnotheras 



where one form has not passed into another form, but each one has originated separately. 

 Some points, however, carefully chosen, may establish unlooked-for differences. Thus 

 the situation of the sole surviving seed is constantly parietal in the Hamaraelidacese and 

 axial in the CaprifoliacesB. 



parietally or axially borne seed, there is a strong bias towards the use of this character 



Hence in the Cornaceae, where genera occur with 



ndicator of different origins. 



As 



the tangentially and radially orientated 



• 



R. R. Gates in Bot. Gaz. sliii. (1907) 81-114. 



525-552 



t Anna M. Lutz, Science, xxvi. (1907) 151 

 § F. Keeble in Journ. Gen. ii. (1912) 163. 



