340 BOTANICAL GAZETTE [october 



is the waning activity of the protoplast. The conclusion is that 

 spore-formation is a response to relatively unfavorable conditions 

 on the part of plants whose activity extends through a period long 

 enough to encounter varying conditions. This would make spore- 

 formation possible among one-celled plants , as well as among 

 many-celled plants. 



One of the problems of reproduction, perhaps to be regarded 

 as the most fundamental one, has been suggested by the previous 

 statements. When protoplasts are detached from a parent plant, 

 whether it be a single protoplast called a spore, or a group of pro- 

 toplasts, as in the case of a propagating bud, the whole structure 

 of the parent is reproduced. Of course the essential separation is 

 physiological, which may take place although complete structural 

 separation has not been effected. When one considers the repro- 

 ductive power in a group of active cells isolated from the parent 

 stock, such as gemmae, propagating branches, buds, tubers, bulbs, 

 cuttings, isolated nodes, and even leaf fragments, it becomes evi- 

 dent that reproduction is a function of every active cell, and that 

 it can express itself when certain conditions are supplied. The 

 conspicuous condition seems to be detachment from the parent 

 stock. It is really a restoration of lost parts, and therefore is a 

 form of regeneration, differing in degree but not in kind from what 

 is ordinarily called regeneration. From this point of view, a spore 

 is to be regarded not so much as a specialized reproductive cell, 

 differing in power from other protoplasts, but as a single detached 

 protoplast rather than a group of them, and therefore regenerating 

 all the structures of the body. What induces these detached pro- 

 toplasts, whether single or in groups, to produce a new individual 

 is no more clear than what induces a fertilized egg to produce a 

 similar structure, but both seem to belong to the same category, 

 and that is, a series of divisions that result in a definite structure. ■ 



A further stage in the evolution of spore-formation is the 

 differentiation of sporangia, which needs no discussion in this con- 

 nection. Sporangia are formed under the conditions that favor 

 spore-formation, and not during maximum vegetative activity. 

 They are not formed as parts of the body, awaiting appropri- 

 ate conditions for spore-formation. The fundamental difference 



