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FRANK DUNN KERN 
dependence in the seed plants may have been the absorption of water 
and food materials, the taking up of complex foods being a later de- 
velopment. This is in accord with a theory hazarded by Cowles who 
adds that as a final development there comes the loss by the seeds of 
the power to renew their growth, except when in contact with the host, 
and the development of a univorous habit. 
As intimated in the foregoing paragraph there is evidence indi- 
cating that the parasitic lower plants (bacteria and fungi) have de- 
veloped from independent plants not directly but through intermed- 
iate saprophytism. There are numerous transitional stages from 
autophytes to saprophytes and on to facultative parasites, ending 
finally in obligate parasitism. The development of the capacity to 
take in organic foods in a saprophytic manner seems to be a simpler 
first step for these forms, rather than the absorption of water and food 
materials in a parasitic way, and at the same time the existing forms 
grade into one another along such a probable course of development. 
Even after parasitism is attained there are still degrees of differentia- 
tion. The forms which can continue without sufficient detriment to 
the host to cause its death, and hence their own, are to be regarded as 
on a higher plane of development than those whose aggressive growth 
soon results in death for both host and parasite. Another condition 
which is agreed by many to indicate a high parasitic evolution is the 
physiological dependence upon a very restricted set of hosts. The 
greater the restriction, which may be a single host species, or even a 
variety, the higher the stage of parasitic development. 
Concerning the independent forms which may be looked upon as 
most nearly representing the probable ancestors of such forms as the 
parasitic bacteria and fungi there is general agreement in a broad 
way but naturally differences of opinion upon many important points. 
The probable connection between some dependent and independent 
forms has received definite recognition in the classifications used by 
some taxonomists. Bessey no longer maintains the Phycomycetes 
co-ordinate with the groups of higher fungi but places them in the 
phylum with the tube algae upon morphological grounds. In like 
manner the Synchitriaceae are grouped with the unicellular green 
algae. The series classed as higher fungi are more isolated and retain 
standing as a separate phylum with debate still going on as to their 
relationships and interrelationships. 
In a recent paper Jones has emphasized the fact that the funda- 
