PLANTAGO 



PLANT - BREEDING 



1363 



rich and so treating it that it will hold moisture. Plan- 

 tago Coronopus, the Bucks-horn Plantain, native to Eu- 

 rope, Asia and North Africa, is sometimes eaten as a 

 pot-herb (see p. 697). It is a low perennial, with linear- 

 lanceolate often pinnatifid leaves. It is 

 not in the American trade. P. cordata, 

 of the eastern United States, is offered 

 by one or two dealers in native plants as 

 a subject for colonizing in bogs and mar- 

 gins of ponds. It is perennial, with a 

 stout rootstock, large cordate-orbicular 

 shining leaf-blades, and a slender spike 

 rising 1-2 ft. high and bearing small pink- 

 ish flowers with exserted style and sta- 

 mens. P. major (Fig. 1838) is a very com- 

 mon dooryard weed. There are about 20 

 native or naturalized species in North 

 America. Plantago is the typical genus 

 of the Plantaginacece, a family that con- 

 tains two other genera, both monotypic. 

 Littorella in Europe and northern North 

 America, and Bougueria in the Andes of 

 Peru and Chile. L. jj. B. 



PLANTAIN. See Plantago and Musa. 







PLANTAIN LILY. Funkia. 



I'LANTAIN, RATTLESNAKE, Hiera- 

 m venosum. 



PLANTAIN, WILD. Heliconia Bihai. 



PLANT-BREEDING. Practical agri- 

 culturists the world over have long rec- 

 ognized that animals can be greatly im- 

 proved by intelligent breeding, but it is 

 only within the last century that it has 

 come to be recognized that plants can be 

 improved in the same way. Even yet some 

 of the fundamental principles of plant- 

 breeding are not generally understood and 

 require to be demonstrated experiment- 

 ally. Within recent years, however, gen- 

 eral interest has been awakened in the 

 subject, particularly in this country, and 

 doubtless results of the greatest interest 

 will soon be attained. 



Practical plant-breeding may be said to 

 have begun with the work of Thomas An- 

 drew Knight and Jean Baptiste Van Mons 

 in the early part of the nineteenth cen- 

 tury. Knight was the first to show the 

 practical value of hybridization in the 

 production of new sorts and races. As 

 early as 1806 he wrote: "New varieties of 

 every species of fruit will generally be 

 better obtained by introducing the farina 

 of one variety of fruit into the blossoms 

 of another than by propagating from a 

 single kind." The other most important 

 factor of plant-breeding, that of selection, 

 was first established by Van Mons, a Bel- 

 gian horticulturist who worked mainly 

 with pears. (See Essay 5, "Survival of the Unlike," 

 Bailey.) Since this time many investigators have given 

 time and thought to the ways in which plants may be 

 improved, until at present we have established a fairly 

 definite system which may be followed, with slight 

 variation, in the amelioration and improvement of any 

 plant. 



The plant-breeder must first of all recognize that a 

 thorough knowledge of the plant he desires to improve 

 is of primary importance. The time for haphazard ex- 

 perimenting has long since gone by, and the experi- 

 menter may simply waste his time if his efforts are not 

 well directed. If it is apples or wheat that he desires to 

 improve, all of the varieties of apples and wheat should 

 studied and their qualities recognized. The experi- 

 menter should always have in view a definite improve- 

 ment which he wishes to obtain, and the varieties which 

 exhibit this feature in the highest degree should be 

 selected for the work. If working from the utilitarian 



1838. 



Spike of Plan- 

 tago major 

 commonPlan- 

 tain. Nat.size. 



standpoint, the desirability of having a definite aim in 

 view can hardly be overestimated, as it is only in this 

 way that the breeder can be guided in his selection of 

 the parent stock or stocks. 



Systematic plant-breeding includes two processes 

 largely distinct in their nature: (1) The production of 

 variations, and (2) the fixation and augmentation of 

 desirable variations by methodical selection. 



In order to improve a plant it must be induced to vary 

 in the required direction. If this variation is brought 

 about by some environmental change the same condi- 

 tions are maintained through another generation, and the 

 plants showing the greatest variation in the required 

 direction are again selected, thus gradually leading to 

 a progressive improvement in the character desired. 

 If the variation is produced by hybridization it must be 

 fixed and rendered hereditary by a similar process of 

 selection. Thus, whether breeding by selection alone 

 or by hybridization, these two factors of breeding enter 

 into the process. 



VARIATIONS, How PRODUCED. In general, plants 

 reproduce their main characters unchanged. The sta- 

 bility of the races of our cultivated plants and natural 

 species depends upon this law of heredity, which has 

 been expressed in the aphorism "like produces like." 

 Plants, however, are not fixed and stable beings, but 

 are eminently plastic and variable. Every individual 

 differs from every other individual in some way, just 

 as every individual animal differs from every other 

 individual of the same race. These individual vari- 

 ations which enable us to recognize one plant from 

 another, or one animal from another, and which are 

 inherent in the being itself and not, so far as can be 

 determined, dependent upon environment, are what 

 Darwin termed "indefinite variations," and are now gen- 

 erally known as "congenital variations." If we examine 

 a row of nursery trees of apple or peach we find that 

 every individual may be clearly recognized by some 

 distinctive character. Some trees grow erect and col- 

 umnar, some low and spreading, some branch low, some 

 high, some have large leaves, some small leaves, and by 

 a careful examination numerous other distinguishing 

 characters can be found. It is on these individual 

 variations that the improvement of plants by selection 

 mainly depends. 



It has been found by breeders of both plants and 

 animals that individuals vary greatly in the power of 

 transmitting their characters to their offspring, and 

 this is one of the most important factors in plant- 

 breeding. As an illustration, ten individual cotton 

 plants may be selected which produce an exceptionally 

 long lint of comparatively the same character. If the 

 seeds from each of these ten select plants are planted 

 separately it will be found that the ten plants vary 

 greatly in their ability to transmit this character of 

 producing long lint to their offspring. The entire prog- 

 eny of one plant may revert and produce a much 

 shorter staple than the parent form. On the other 

 hand, one of the original ten plants may have the power 

 of inheritance strongly developed and transmit to the 

 great majority of its progeny the quality of producing 

 long lint; It is to the progeny, then, of this individual 

 that the breeder must look in order to fix a new race of 

 long-staple cotton. The strength of the hereditary ten- 

 dency is thus of the greatest importance to the breeder. 



Another form of variation probably important to the 

 plant-breeder is that caused as a direct result of envi- 

 ronment and termed by Darwin definite variation, be- 

 cause all plants subject to the same environment tend 

 to vary in the same direction. As an illustration, plants 

 removed from a low altitude to a high altitude become 

 dwarfed in stature and the flowers become larger and 

 usually brighter colored. Transferring the plant to the 

 seacoast and growing it under maritime conditions usu- 

 ally results in the leaves becoming thicker and the 

 whole plant more succulent. If such plants are trans- 

 ferred back to the interior, away from all effects of the 

 sea, the next year they usually, if not always, revert 

 entirely to their original characters. If, however, they 

 are grown in a maritime region for several generations 

 and the seed is selected every year from the most suc- 

 culent individuals, it is believed that a succulent sort 

 may be originated more quickly than in any other way. 



