1918] DUDGEON—RUMEX CRISPUS 413 
occurs during the reduction divisions. When the differentiation is 
pushed farther back, however, until the sporophytes producing the 
two kinds of spores are likewise differentiated, it is difficult to see 
how chromatic constitution can be made to explain the situation. 
It is to this later and secondary phase of sex segregation that the 
term dioecism is applied in seed plants. The view has been 
expressed in scattered papers that the particular species under 
investigation have been rendered diclinous by failure of either 
the stamen or the ovules to produce functional gametophytes, and 
that this process has been carried a step farther, to the complete 
suppression of the functioning stamens in some (ovulate) plants, 
and to the complete suppression of functioning ovaries in other 
(staminate) plants. This view has been occasioned by the dis- 
covery that more or less perfect essential organs may produce 
few or no functional sexual products. 
Rumex seems a particularly favorable group for the study of 
this process, and it is believed that it shows convincing evidence for 
the origin of dicliny, and finally of dioecism, by degenerations 
during ontogenesis. The members of the section LAapAtHuM, 
including R. crispus, are variously described in manuals as having 
hermaphrodite, polygamo-monoecious, polygamo-dioecious, andro- 
monoecious, gyno-dioecious, etc., flowers, while those belonging to 
the AcETosa section are described as dioecious. In R. crispus, at 
least, the appearance of the mature flowers evidently is misleading, 
for sections show that the apparently perfect flowers are almost 
invariably functionally staminate; the apparently staminate 
flowers are really such; while the apparently ovulate may be 
either functionally ovulate or completely sterile. These conditions 
are brought about by degeneration at various stages in oogenesis 
and spermatogenesis, and not by arrested development. The 
result, even in the aieiiarese perfect flowers of R. crispus, is physio- 
logical dicliny. 
Rot (8) found in species of section AcETosA, which are 
usually exclusively dioecious, that sometimes hermaphrodite and 
even staminate flowers are produced, but that the pollen is defective 
in every case; others have found the same situation. All the species 
in section LAPATHUM that he investigated produced hermaphrodite 
