332 BOTANICAL GAZETTE [way 
being of different lengths. The same thing has since been found 
to be the case in several other plants having morphological differ- 
ences in their chromosome group. GEERTS (9) published two 
figures indicating that in Oenothera, in which the chromosomes 
exhibit no morphological differences (that is, are isomorphic), 
they are also in pairs in the somatic tissues. Two figures (9 and 
10) in a subsequent paper of mine (GATES 5) show indications of 
the same thing. Therefore, though this cannot be so clearly 
demonstrated in organisms whose chromosomes are isomorphic, 
yet it cannot be doubted that the chromosomes are in homolo- 
gous pairs throughout the somatic cells. OvERTON (17) gives 
indications of this in Thalictrum (pl. 1, fig. 1), and believes (p. 45) 
that the homologous parental elements are finally brought side- 
by-side in the somatic nuclei. CrtEMENS MULLER (16) has recently 
given a particularly clear demonstration of this paired arrange- 
ment, from studies on the root tips of Yucca species, in which the 
chromosomes are either very long or very short. 
From these results it is evident that the pairing of homologous 
chromosomes is not brought about at synapsis or any other peri 
of meiosis, but that the chromosomes are really paired throughout 
the life cycle of the sporophyte. The pairing must therefore have 
taken place at the time of fertilization. One of the best com- 
tributions that could be made to the study of the life cycle would be 
the determination of just how the two single sets of x chromosomes 
in the egg and sperm nuclei become, in the nuclei descended from 
the fertilized egg, a set of 2x chromosomes arranged in homolo- 
gous pairs. The idea that the final act of fertilization, that 1 
the pairing of homologous chromosomes, is deferred until synaps!s, 
an idea which has been often expressed, is therefore a mistaken one 
and views of synapsis and its importance in the life cycle will have 
to be modified accordingly. The view that the function of synaP- 
sis is to bring about a pairing of chromosomes or of spirems is no 
longer justified, (1) because the chromosomes are now known t0 
be paired throughout the somatic tissues of the sporophyte, (2) 
because there is no satisfactory evidence of a smaller unit of struc 
ture within the chromosomes whose union or exchange could be 
brought about if the materials were stretched out into slender 
