1 88 



Garden and Forest. 



[April 17, iS 



Plant Patents.— It is certainly desirable that the originator of 

 varieties should be protected. But I cannot see that plant- 

 patents could be feasible, even if possible. In the first place, 

 it is exceedingly doubtful if a patent could be had for those 

 varieties which spring up from a chance seeding, and it is 

 a fact that most of our varieties come in this way. But 

 granted the patent, there are cases innumerable in which no 

 jury, even of experts, could agree concerning the identity or 

 distinctness of varieties. There are those who contend that 

 no two varieties can be alike if they originate in different 

 places, even though there are no characters to separate them. 

 Of this class is Jacob Moore, perhaps the leading advocate of 

 plant-patents, and he argues that expert growers will not con- 

 found such varieties. The facts, however, are against this 

 theory. On the whole, there appears to be no better way 

 than for the originator to adopt more business-like methods 

 of handling his new sorts, and to sell under a copyrighted 

 trade-mark. 



Cornell University. L. H. Bailey. 



Principles of Physiological Botany, as Applied to 



Horticulture and Forestry. 



XVI. — Hybridization. 



T N what we have called cross-breeding, we keep within the 

 ■'• limits of the species, using the pollen of one variety to act 

 on the pistil of another variety of the same species. And, of 

 course, we can cross races in the-same way. 



Now if we pass beyond tiie confines of the species and at- 

 tempt to cross two different species, using the pollen of one to 

 act on the pistil of another, we are undertaking what is known 

 as hybridization. A hybrid is a cross between two species. 

 The term has, however, been rather loosely applied ; in fact, 

 some writers have included crosses between varieties as hy- 

 brids, and such variety-hybrids frequently figure as true hy- 

 brids in some catalogues of plants. In the present paper it is 

 designed to restrict tlie word wholly to crosses between what 

 are accepted as true species. 



First, as to the occurrence of hybrids in nature, little need 

 now be said. That there are some well-marked hybrid Willows 

 and hybrid Oaks is generally believed by all botanists, but the 

 evidence on which such conclusions rest is, of course, infer- 

 ential. Therefore it is better for us to turn at once to the con- 

 sideration of artificial hybridization and note its methods as 

 well as its results. 



The method is simple theory, and not difficult to put into 

 practice. The flower which is selected as the female is care- 

 fully freed from all of its stamens, with their pollen-bearing 

 anthers, and then its stigma crowning the pistil is to be care- 

 fully dusted by pollen from the flower selected as the male. 

 The transfer of the pollen can be effected by means of a sable 

 pencil or camel's-hair brush. It is not necessary in all cases 

 that the pollen should be absolutely fresh, for the pollen of 

 some plants can maintain its vitality for a long time, but care 

 must always be taken to see that the pollen is perfectly ripe. 

 Moreover, the sdgma of the pistil to which the pollen is ap- 

 plied must be just mature and receptive. If it is not mature, 

 or if it has passed its period of complete receptivity, the pollen 

 will not have its full effect; in fact, it would probably not fiave 

 any effect at all. 



After application of the pollen has been made, care must be 

 observed that all insects are excluded, and that no foreign 

 pollen is conveyed in any manner to the flower. Further than 

 this, no special caution need be exercised. If impregnation 

 has been effected the seeds will "set," and the fruit will go on 

 to ripeness. It is worthy of note that in many cases of hybrid- 

 izing, the fruit will apparently ripen and the seeds will seem to 

 to be good, while in point of fact they are worthless. In gen- 

 eral it should be said that, in hybridizing, the blanks are many 

 and the prizes are few. 



The range of selection of species between which this pro- 

 cess can be tried with a fair chance of success is wide. It is 

 not possible, however, to state beforehand whether a given 

 trial will prove successful, for there are some instances in 

 which the process is not even reciprocal ; that is, there are 

 cases in which the species A can be used with success as the 

 female element in the experiment, but will utterly fail if it is 

 employed as the male, whereas the species B may behave in 

 just the opposite manner, being capable of furnishing pollen 

 which will be efficient, while its pistil might not prove recep- 

 tive. 



In general, the species selected should be nearly related. 

 There are a few cases on record in which species belonging 

 to different though closely allied genera have been success- 

 fully crossed, but it may well be that the limits of such genera 



are yet to be changed by systematic botanists. This has al- 

 ready been done in the well-known genera Azalea and Rhodo- 

 dendron. Certain species of these two genera can be made to 

 cross with each otlier, and their cases have formerly been 

 cited as showing that different genera can be hybridized. Re- 

 cent classification, however, has placed these two genera under 

 one head, and the two are now known as Rhododendron. 



It is an interesting fact that frequently in a genus there is 

 one species which seems particularly well adapted to serve as 

 the male or fe'male factor in hybridization. Among the Rho- 

 dodendrons the species called Rhododendron Catawbiense has 

 played this part in the innumerable successful crosses with the 

 tender species of the Himalayan Mountains. 



Hybrids generally share, but not in an equal degree, the 

 characters of the two parents. In some instances a sort of 

 average is struck between the two ; this, however, is rare. 

 The influence of one of the two parents is sometimes so pre- 

 ponderating that the effect exerted by the other can hardly be 

 discerned. This was the case in the well-known cross pro- 

 duced by Mr. Francis Parkman between the two species, 

 Lilium speciosum (lancifolium) and Liliuin aicratum. Of the 

 offspring from this cross only a single plant shared to any 

 marked degree the characters of the two .parents, but the won- 

 derful and beautiful exception appeared to combine, in almost 

 equal amount, the striking and desirable peculiarities of both. 



.^s a rule, the roots, stems and leaves of hybrids are stronger 

 and the flowers are more showy than those of either parent, 

 but there is a marked diminution in the reproductive power. 

 Hybrids incline to be sterile, but this sterility is by no means 

 complete. There are many cases of fertile hybrids. 



The offspring of hybrids possess a remarkable tendency to 

 vary. The progeny have been said to cut adrift from the an- 

 cestral moorings, and they appear to drift passively in subse- 

 quent generations. This curious fact has been made use of 

 by cultivators who have desired to obtain variant forms. They 

 first of all secure a fertile hybrid, and employ this for careful 

 seed-breeding. 



Since hybrids are so rarely wholly fertile and, besides this, 

 have a marked tendency to vary in their offspring, it is gen- 

 erally best to propagate by means of their buds in some way. 



Derivative hybrids are those which result from the union of 

 a hybrid with one of the parent forms or with a hybrid from a 

 totally different source. In all these cases there is a tendency 

 towards reversion to one of the ancestral types. 



One of the most puzzling cases of blending of different char- 

 acters is that known as graft-hybrids. When some of the va- 

 riegated forms of Abutilon have been grafted on green-leaved 

 forms, a few of the subsequent shoots of the stock have been 

 more or less affected by the variegation. The most remark- 

 able case of this is that of Cytisus Adami* a plant which pre- 

 sents a form midway between Cytisus Laburnum and Cytisus 

 purpureus. While there are many who believe that we have 

 here a case of a hybrid produced by seed, the history as orig- 

 inally given indicates that the blending resulted from placing 

 a bud of the former in the stem of the latter. The case is not 

 wholly without its bearing on what has been noticed in some 

 of our fruit-trees. 

 Cambridge, Mass. George Lincoln Goodale. 



Recent Publications. 



A Mamial of Orchidaceous Plants. James Veitch & Sons. 

 Part IV. Cypripedium. London, 1889. 



The present number of this excellent publicadon is de- 

 voted to a description of the tropical Cypi-ipediums, which are, 

 perhaps, just now occupying the attention of the horticultural 

 world more strongly than any other class of plants. We can- 

 not give a better idea of the general characteristic of the work 

 and the method in which the subject is treated than by laying 

 before our readers some rather extended quotations from its 

 pages, which abound in interesting information and sound 

 practical advice. After speaking of the fact that the peculiar 

 structure of the flower of the Cypripedium shows that many 

 relative or intermediate forms have been swept away, leaving 

 this single genus as a record of a former and more simple state 

 of the great Orchidaceous order, the author goes on to show 

 "that the structure of the flowers does not furnish the only 

 evidence of the Cypripedes being a more primitive race of 

 Orchids than any other existing forms. The geographical dis- 

 tribution of the genus, especially of the two sections of it that 

 form the subject of these pages, reveals some remarkable 

 facts respecting the present history of the included species, all 

 of which tend to the conclusion that the individual plants com- 

 prising them must at one time have existed in great numbers, 



* See Gray's Text-Book, vol. 2, p. 445. 



