DEVELOPMENT OF MORPHOLOGICAL CONCEPTIONS 9 



terms of sporogenous tissue, without reference to the presence or 

 absence of a morphologically constant wall; of archegonia as axial 

 rows of potential eggs, without concern for an exact morphological 

 definition of the sterile jacket. The main question is, what deter- 

 mines the formation of sporogenous tissue rather than of sporangia; 

 what determines the formation of eggs or sperms, rather than of 

 archegonia and of antheridia? 



(2) The Possibilities of Primordia. This has to do with what I 

 have called the doctrine of predestination. It is more than a ques- 

 tion as to the variable form or structure of an organ; it is a question 

 as to the variable nature of an organ that may arise from a given 

 primordium. When primordia that usually develop microsporangiate 

 organs produce megasporangiate ones, or vice versa; when the same 

 plant body produces sporangia or gametangia in response to con- 

 ditions imposed by the experimenter; it becomes evident that pri- 

 mordia may be indifferent not only as to form, but also as to nature. 



This meant a general unsettling of morphological conceptions. 

 To find, for example, that a given cell is not set apart from its first 

 appearance to function as an archesporial cell, but that there are as 

 many potential archesporial cells as there are cells in an extensive 

 tissue; and further to find that the archesporial cell when discov- 

 ered by its functioning does not necessarily produce all the sporoge- 

 nous tissue, is to abandon the idea of predestination and of defining 

 structures on a rigid morphological basis. 



(3) The Origin of Species. Probably the greatest triumph of 

 experimental morphology thus far is that it has put the problem of 

 the origin of species upon an experimental basis. The ability to vary 

 and to vary promptly and widely, when considered in connection 

 with structures used by taxonomists, means new species under cer- 

 tain conditions. To analyze these conditions is a problem of enormous 

 complexity, but to have the problem clearly before us is but the 

 prelude to its solution. There is still a tendency to call things inher- 

 ent that are not apparent, but this is a habit not easily outgrown, 

 and such a problem as the origin of species will long have its con- 

 venient category of "inherent tendencies." 



Certain conclusions are inevitable as one considers the perspective 

 opened by experimental morphology. 



In the first place, it would seem that what we have called "bio- 

 logical laws" are also the laws of physics and chemistry, and the 

 experimenter must be prepared to use all the refinements of method 

 developed by physicists and chemists. Much of the work done in 

 the name of experimental morphology is as yet crude in the extreme, 

 and we are often left with a confusing plexus of conditions rather 

 than with a satisfactory analysis. To grow plants, to observe certain 

 results, and to draw conclusions, too frequently means the arbitrary 



