The other phase of the problem is concerned with the manner in which the single elementary species and varieties have sprung from one another. There is no reason to suppose that the world is reaching the end of its development, and so we are to infer that the production of new species and varieties is still going on. In reality, new forms are observed to originate from time to time, both wild and in cultivation, and such facts do not leave any doubt as to their origin from other allied types, and according to natural and general laws. In the wild state however, and even with cultivated plants of the field and garden, the conditions, though allowing of the immediate observation of the origination of new forms, are by no means favorable for a closer inquiry into the real nature of the process. Therefore I shall postpone the discussion of the facts till another lecture, as their bearing will be more easily understood after having dealt with more complete cases. These can only be obtained by direct experimentation. Comparative studies, of course, [463] are valuable for the elucidation of general problems and broad features of the whole pedigree, but the narrower and more practical question as to the genetic relation of the single forms to one another must be studied in another way, by direct experiment. The exact methods of the laboratory must be used, and in this case the garden is the laboratory. The cultures must be guarded with the strictest care and every precaution taken to exclude opportunities for error. The parents and grandparents and their offspring must be kept pure and under control, and all facts bearing upon the birth or origin of the new types should be carefully recorded.