No. 464] STUDIES ON PLANT CELL.— VII. 583 
idioplasm may be separated so purely by the longitudinal split- 
ting of the single (fusion) spirem or through the distribution of 
unmodified sporophytic or somatic chromosomes as to give abso- 
lutely and relatively pure germ cells through Mendelian laws. 
Allen's discussion, very briefly summarized above, is impor- 
tant for the emphasis which is laid upon the significance of a 
possible mixing of the parental idioplasms in the more or less 
complete union of chromatic material, which is generally recog- 
nized as characteristic of synapsis. There is a general tendency 
to rest content when the chromosomes are accounted for as 
units while they are merely the grosser form of expression of 
the idioplasm whose final architecture is intricate far beyond our 
present powers of analysis. Allen's own studies upon the events 
of synapsis in the lily with the regular fusion in pairs of chromo- 
meres of different parentage may well cause one to hesitate in a 
full acceptance of the chromosome as fixed and unchanged in its 
organic constitution throughout the life history. The phenome- 
non of hybridization is far too complex to be explained in terms 
of simple ratios and while some characters may be paired or 
correlated in proportions that can be expressed by mathematical 
formulz there is little probability that the assemblage of charac- 
ters which make the species can be so definitely grouped as the 
strongest disciples of Mendel may hope. However, a great 
forward step has been taken and we may expect important 
results from the empirical methods so clearly defined by Mendel 
and by the close investigation that cytologists are making 
of the history of idioplasmic structures (chromosomes) during 
ontogeny. 
8. XENIA. 
Xenia is the “immediate or direct effect of pollen on the 
character of seeds and fruits." The term was first proposed by 
Focke, in 1881, and is now well established. Xenia has long 
been known to the plant breeder as one of the most interesting 
and puzzling problems of hybridization. The botanist has nat- 
urally looked for the results of hybridization in the development 
of the embryo from the seed since: this structure has received 
