June 19, 1893.] 



Garden and Forest. 



243 



inaugurating work on this line, and lie has shown some- 

 thing of its importance and value. But such a work should 

 not be left to one man. It is sufficiently important to com- 

 mend itself as a field of cooperative effort by botanists all 

 over the world. Our cultivated varieties of esculent plants 

 have come from widely different sources and conditions. 

 Even those most closely related have often sprung from 

 very different environments. From this it is likely to fol- 

 low that their adaptations at the present time are quite 

 different. The only possible way to classify these varieties 

 and arrive at anything like reliable conclusions concern- 

 ing them is by means of the plants themselves. In most 

 cases it is impracticable to have access to all the growing 

 plants needed for any such attempt, even if the desired 

 forms are all still in existence, which ordinarily is not the 

 case. Herbarium specimens, while sometimes misleading, 

 are still the most practicable means of arriving at the end 

 in view^. Every one who has had occasion to give special 

 attention to any one group of plants has, doubtless, realized 

 the importance as well as the dearth of material of this 

 kind. 



Such material, if easily accessible, might, in some cases, 

 afford the means of detecting an old variety when brought 

 forward under a new name. This could not be'done in a 

 majority of cases, but in most cases it would be possible 

 to determine the relations, parentage, and even the strains, 

 from which the new variety has sprung, and thereby in 

 great measure to predict what its usefulness is likely to be. 

 Every practical grower knows what inherent differences 

 are to be expected between a Gooseberry or a Red Rasp- 

 berry of American parentage and one of foreign parentage. 

 It is needless to say that the herbarium method of study- 

 ing cultivated plants is the inveterate enemy of all horticul- 

 tural frauds. When the position and relationships of a 

 plant are accurately known, its possible attainments can 

 also be pretty well determined, and any exorbitant claims 

 which may be made for it can be easily refuted. 



The value of such specimens for purposes of illustration 

 in the class-room ought not to be overlooked. Every 

 teacher of horticulture doubtless finds that very many of 

 our cultivated fruits and vegetables even are wholly un- 

 known to a considerable proportion of his students. 



Individual effort along such a line as this is not sufficient, 

 however. There ought to be hearty cooperation between 

 every experiment station in the country. Exchanges are 

 easily made, and if those station workers who have good 

 facilities for collecting any class of plants vifould collect in 

 sufficient numbers to supply them liberally to others so 

 located that this same line is not readily available, it would 

 not be a difficult task for every station to obtain a very 

 satisfactory collection of the cultivated plants of our own 

 country, or even of the greater part of the world, in course 

 of time. It is greatly to be hoped that such work may 

 receive additional attention from horticultural workers in 

 future. 



Experiment station, Lincoln, Nebraska. "• ''• C(Z/ (Z. 



Hybrid Birches 



NATURAL hybrids among Oaks, and more especially 

 among Willows, are now known to be of such com- 

 mon occurrence that botanists are always prepared to find 

 them. The Birches rank among many other groups of 

 trees and shrubs in which natural hybrids have been col- 

 lected and described. Perhaps the best notice of hybrid 

 Birches is to be found in the late Dr. E. Regel's vi^ell-known 

 monograph of the Betulacea;, published in Moscow in 1861, 

 in which Betula hybrida is described as a hybrid between 

 B. alba and B. nana, and other intermediate forms are 

 mentioned. Regarding his B. hybrida, Dr. Regel says that 

 specimens which he considered as the hybrid between 

 B. alba and B. nana he had seen from the Jura of Switzer- 

 land, from the flora of St. Petersburg, from Siberia (Tschuja, 

 Altai), and from Sweden (Torneo and Karesuando in Lap- 

 land), partly in forms strictly intermediate, partly in other 



forms which approach either B. alba or B. nana. Dr. Regel 

 also states that Koch considered some of the described 

 forms as B. intermedia, Thomas, between which also really 

 intermediate forms are found, which show their origin, since 

 the fertile hybrid in the next generations more or less 

 quickly revert to one of the ancestors. There does not 

 appear to have been published any notice of hybrids of 

 Betula in North America, and this note is to record some 

 apparent hybrids between the shrul)by B. pumila and B. 

 lenta, the Black or Cherry Birch, which becomes one of 

 our fine trees. 



Betula lenta is an abundant native tree in the Arnold 

 Arboretum and adjacent country, but B. pumila is rare in 

 eastern Massachusetts. It has, however, been freely intro- 

 duced into the Arboretum by seed collected in other parts 

 of New England. 



From a vigorous plant of this Dwarf Birch, which was 

 growing about one hundred paces to the east of a number 

 of healthy, well-grown trees of Betula lenta, a large quan- 

 tity of seed was collected in the autumn of 1887. This was 

 sown in January, 1888, and resulted in several thousand 

 seedling plants. As these grew, a large number were dis- 

 posed of or destroyed. Out of several hundred plants which 

 have been kept to maturity half a dozen indi\'iduals show 

 distinct characters, indicating hybridity with B. lenta, the 

 only species growing in the vicinity and the pollen of 

 which would be directly blown to the seed-plant by the 

 prevailing westerly winds. 



The very short, erect, usually solitary and axillary cat- 

 kins of flowers of Betula pumila, the short fruits, not often 

 over half an inch long and generally much less, and the 

 bluntly dentate, generally obovate or rounded leaves, 

 which hardly average more than an inch in length, are in 

 striking contrast to the large terminal staminate aments of 

 B. lenta, to the long aments of the fertile flowers, the thick 

 fruits, often nearly an inch in length, and the large, long- 

 pointed, sharply serrated leaves. Moreover, the Dwarf 

 Birch is always a slender shrub, from two or three to seven 

 or eight feet high, while our Black Birch is one of our finest 

 trees of the genus. 



All of the hybrids noticed show a distinctly different 

 growth in comparison with the Betula pumila among 

 which they are growing. They are mostly more vigorous 

 in stem and branch, becoming taller and larger bushes, and 

 one or two may develop an arborescent character, although 

 they already flower and fruit freely, as several of the 

 hybrids have done for two or three years. 



Four of the hybrids possess very distinctly the pleasant 

 aromatic flavor and fragrance which is so characteristic of 

 the twigs and inner bark of the Black Birch, the degree of 

 the aromatic quality varying in different individuals of the 

 hybrids, although it is not quite so rich in any of them as 

 in the typical Black Birch, while two of the hybrids have 

 little or none of the aromatic principle, in this respect 

 agreeing with Betula pumila. 



The leaves of all the aromatic hybrids are intermediate 

 in size between the typical leaves of the parents, but by 

 their lustre, general ovate form and the unequal sharp ser- 

 rations of the margins they have more resemblance to 

 Betula lenta than to B. pumila. In the blossoming and 

 fruiting the specimens are also intermediate. In some the 

 sterile catkins are terminal, as in B. lenta, although hardly 

 a third the length of those of this species ; in others the 

 sterile catkins are axillary and below the fertile flowers, in 

 this resembling B. pumila, although two or three times 

 as long, and beeoining recurved or pendulous as they 

 elongate. At flowering the intermediate condition is very 

 apparent, and it shows itself even in the winter buds. In 

 the fruitage a very marked variation is shown in general 

 size and form, and the scales show intermediate states be- 

 tween the heavy three-lobed scales of B. lenta and the 

 lighter, more deeply cleft scales of B. pumila. 



By the color of their twigs, absence of aromatic quality, 

 the obovate tendency in the shape of many of the leaves, 

 their blunter, more angular dentation and paler color be- 



