December 30, 1896.] 



Garden and Forest. 



523 



(2) That Maize, as we now know it, owes its origin to the 

 crossing of Teosinthe, as one of the parents, with the pollen 

 of an extirpated closely related grass, and that the prog- 

 eny of this cross by variation under cultivation produced 

 ears of considerable size, with kernels of great nutritive 

 value. If this hypothesis is accepted, then the proposition 

 is proven that many species, which are botanically recog- 

 nized as such, have had a hybrid origin, as, for example, 

 the contested case of Bartram's Oak. 



Dr. J. M. Macfarlane's observation as to the possible 

 origin of species from hybrids is apropos : 



Hitherto it may be said that authorities, with few exceptions, 

 have declared wholly against the view that hybrids may be 

 sufficiently fertile, and their progeny sufficiently strong and 

 adaptable to be fitted for survival, not to say increase, in the 

 struggle for existence. The admirable experiments conducted 

 by Wichura on Willows go far to prove, one would think, that 

 by the fourth or fifth generation enteeblement and decay be- 

 come so marked that continued production fails. But against 

 this is to be placed the fact that many of our horticulturists are 

 ardent believers in the continued tertility of hybrids, as witness 

 the article by Professor Meehan, already cited, although we 

 believe an oversanguine expectation is sometimes entertained 

 under this head.* 



When one finds the undoubted hybrid between Geum rivale 

 and G. urbanum, frequently described by systematists as a spe- 

 cies, and that in many places the hybrid is nearly or quite as 

 abundant as either parent, that it freely produces good seeds, 

 and further that it has, as we have already indicated, many 

 points of superiority as a combined organism which neither 

 parent possesses separately, we have good reason for the exer- 

 cise of caution before pronouncing decisively against species 

 production from hybrids. 



(3) That Indian Corn is the result of a cross between 

 Teosinthe and a race or variety of the plant produced by 

 successive cultivation of the wild plant until its characters 

 as a variety or a race have become fixed. This may have 

 taken place under irrigation, where the conditions of growth 

 are more or less under absolute control. It is probable that 

 the early cultivation in Mexico began as a shallow scratch- 

 ing of the soil for water distribution, and that the early cul- 

 tivation was near the springs and watercourses. As many 

 of these rise in the hills, hill or mountain culture was the 

 first practiced. The wild plants, therefore, chosen for such 

 cultivation would under such feeble farming tend to vary 

 but slightly from the original form. As the population, 

 however, grew more dense and the water privileges possi- 

 ble through this imperfect system of irrigation more 

 restricted, new methods of engineering were of a necessity 

 adopted by the primitive husbandman. Deeper and longer 

 ditches were dug, reservoirs constructed and cultivation in 

 the lower-lying levels thus became possible through better 

 water distribution and impounding. That this was the way 

 in which cultivation by irrigation began is proved by the 

 ancient irrigating works to be found on the hills long since 

 abandoned. Such are to be found in Seriland, according 

 to the observations of Professor W. J. McGee, of the Bureau 

 of Ethnology f With the more extensive cultivation in 

 the valleys through a better regulated water-supply, the 

 plants naturally lost their feral characters and became more 

 and more domesticated in appearance. It is at this point 

 in the culture of plants, when agricultural methods have 

 become more or less stable, tnat the fixation of certain 

 races or varieties of field plants may be said to have taken 

 place. Such a fixation of Teosinthe, as an agricultural 

 race, may have taken, or probably did take, place. It was 

 then that the presupposed cross between Teosinthe and its 

 variety occurred. That this cross would produce some 

 interesting results is corroborated by the behavior of other 

 plants. Spontaneous hybrids are, as a rule, much more 

 variable than those produced artificially — for example, Ver- 

 bascum lychnitis x Thapsus and V. lychnitis x nigrum. 

 Professor Bailey J says : 



You want varieties quickly, and they must be distinct. You 



turn at once to hybridization. Hybridization is nominally rare. 

 There is no proof that nature made a species or potent form 

 in this way.* But she mildly crosses one species with itself, 

 and out of the slightly variable offspring selects those which 

 are best adapted to the place in which they live, and uses them 

 for the subjects of another congenial cross, and so the family 

 marches on from generation to generation, each step slow, 

 but each one sure. 



It is probably in such a manner that our cultivated Corn, 

 originally a cross breed, f may have arisen. 



The specimens which were grown in Philadelphia during 

 the season of 1896 from seed of the fourth hybrid, or, ac- 

 cording to the last view expressed, fourth cross-bred 

 generation, followed, in their vegetative parts, the horticul- 

 turist's rule,J that 



Crosses of different races and species are distinguished from 

 plants of a pure race, as a rule, by the power of vegetation. 

 Hybrids between very different species are often very weak, 

 especially when young, so that it is difficult to successfully 

 raise the seedlings. On the other hand, crosses of more 

 closely related species and races are, as a rule, uncommonly 

 luxuriant and strong; they are distinguished mostly by size, 

 rapidity of growth, early dowering, abundance of flowers, 

 longer life, stronger reproductive power, unusual size of some 

 special organs, and like characteristics. 



The Philadelphia plants reached a height of twelve feet, 

 grew rapidly, were of long life and produced at nearly all 

 of the nodes below the ears strong aerial roots. 



If we consider Indian Corn to have arisen as a cross- 

 breed, or hybrid, we have an explanation aS to many of 

 the teratological specimens of Corn frequently found in 

 field and garden cultivation. These teratological appear- 

 ances may be explained by reversion, or may be simple 

 malformations It is a well-known fact that malformations 

 and curious forms are much more common, especially in 

 the flower parts of hybrids, than in individuals of pure 

 descent. 



In conclusion, if the latter supposition is the correct one, 

 it is probable that the wild ancestor of Maize is the 

 Teosinthe, Euchla?na Mexicana, because nature avoids 

 hybridization on account of the sterility of the offspring, 

 thus generally precluding the possibility of a cross between 

 tvvo distinct genera or species, and, secondly, because it is 

 found by common experience that the fertility of a plant is 

 increased by crossing two varieties of the same species 

 which have been produced under differing conditions, 

 or in different geographical localities, such as would be 

 found in the case of Teosinthe and the agricultural race 

 produced through successive advances in methods of irriga- 

 tion. If the above view is not accepted, the fact that 

 Teosinthe and Maize can be crossed and a fertile progeny 

 result shows that the two plants are united by the close 

 and intimate bonds of kinship. 



University of Pennsylvania. _/• " • H dlillberger. 



Landscape Effects at Kew. 



THAT part of Kew which formerly was known as 

 "The Wilderness,'' or Pleasure-grounds, and which 

 is now designated The Arboretum, consists of about one 

 hundred and eighty acres of what is now by far the most 

 picturesque scenery in the gardens. In 1850 Sir William 

 Hooker was instructed to take charge of it and form "an 

 arboretum, or classified collection of hardy trees and shrubs 

 on a scale worthy of the nation." It was then "a large 

 area of wooded and scrubby ground devoid of interest or 

 picturesque effects"; it is now richly stocked with trees 

 and shrubs from all parts of the world, and at the same 

 time it is " a paradise of trees ami song-birds, shady glades, 

 well-planned vistas, bold sweeps of green lawns, and set 

 in the midst of it a lake whose banks and islands are so 

 skillfully planted with tastefully grouped tree and shrub 

 and herb that artists of repute spend months in making 

 pictures of the views it affords. The lake was made by 



* 1892. Transactions Royal Socitly of Edinburgh, xxxvii., 



t Science, N. S., ill., 493. 



t 1896. L. H. Bailey, J he Survival of the Urilike, 177. 



283. 



* Vide ante. 



t Vide ante, foot-note. 



t 1895. L. II. Bailey, Plant Breedings -3 



