July 4, 1894.] 



Garden and Forest. 



263 



sufficient data could be gathered to show that any varieties are 

 practically dioecious. ... I have found some groups entirely 

 without pistils for a series of years, and last year I was surprised 

 to find no pistils on my Gaylord trees that had never refused to 

 bear before. They are loaded again this year." In the last 

 Report of the Minnesota Horticultural Society, Mr. Lord ob- 

 serves further, "Nearly all native Plums produce an abun- 

 dance of pollen, but some varieties are more or less deficient 

 in stigmas every year, and in some years are entirely deficient. 

 This habit is, I believe, peculiar to some varieties, not only 

 when indigenous or growing wild, but when transferred to 

 other localities, the habit is intensified, so as to produce im- 

 perfect stigmas, or, perhaps, none at all. . . . I have a group of 

 trees that blossom profusely every year that never has pro- 

 duced any fruit, growing within a few rods of another group 

 that has borne nearly every year for forty years. The blos- 

 soms of the first-named group bear no stigmas, many of the 

 blossoms not even having the rudiments of one. But I was 

 greatly surprised this year to find no stigmas in the blossoms 

 of some kinds that have borne fruit for several years in suc- 

 cession until this year, from which I conclude that there is a 

 wide field in this direction for experiment and investigation." 



Certain varieties, as the Wild Goose and Mariana Plum, that 

 are productive further south, are rarely fertile in Wisconsin, 

 and these showed a low percentage of perfect flowers in our 

 Plum orchard. This suggests that the failure of pistils may be 

 due, at least in some varieties, to severity of climate. I think 

 it possible that poverty of the soil and overbearing may in 

 some cases cause sterility in Plum-blossoms. Air. Waite, in 

 his investigation of the fertilization of Pear-flowers, came to 

 the conclusion that this is true in the Pear. It is also possible 

 that partial destruction of the foliage by insects or fungi 

 during the growing season may sometimes cause sterility of 

 the flowers, for while a checking of growth in a moderate de- 

 gree doubtless tends to the production of flower-buds, an 

 excessive check might so impoverish the tree that there would 

 not be sufficient stored food to develop fruit. 



In conclusion, I wish to call attention to the advantages that 

 are likely to result from hybrids between the hardier varieties 

 of the European Plum and the more prolific varieties of 

 Prunus Americana. If we can combine the robust pistils of 

 the former species with the cold-enduring qualities of the lat- 

 ter, we may hope forannual crops. Of the European varieties in 

 ourown Plum orchard Moore's Arcticappears to be the hardiest, 

 and of the Americana sorts, Forest Garden is now carrying the 

 largest crop. 



Madison, Wis. ■£•■ o. LrOff. 



Flora of Central Thibet. 



THE following account of this interesting flora is taken 

 from a late number of the Kew Bulletin : 



Previous to Colonel Przewalsky's explorations little was 

 known of the flora of the vast country lying immediately 

 north of the Himalayas, generally known as Thibet ; and only 

 portions of his discoveries have been published. Sir Joseph 

 Hooker penetrated the fringe of this country on the Sikkim 

 frontier ; Dr. T. Thomson, Lieutenant-General Strachey and 

 Mr. J. E. Winterbottom botanized the extreme west. That was 

 upward of forty years ago. Since then various other travelers 

 have entered the country for short distances at various points, 

 and the rich flora of the extreme east has been made known 

 through the extensive collections sent to Europe by Father 

 David, Mr. Pratt, Prince Henry of Orleans and others. 



Captain Bower's journey across Thibet from west to east, 

 in latitudes between thirty-four and thirty degrees, and Mr. 

 Woodville Rockhill's journeys from north to south, in about 

 the longitude of Lhassa, are so well known that it is only neces- 

 sary to mention them in connection with the plants connected. 

 Surgeon-Captain W. G. Thorold accompanied Captain Bower 

 and made a collection of all the plants found growing at eleva- 

 tions between 15,000 and 19,000 feet. Mr. Rockhill also collected, 

 and his plants, as well as Mr. Thorold's, were presented to 

 Kew, as announced in the Kew Bulletin (1893, p. 369). 



These collections, together with a smaller one made by 

 Captain H. P. Picot, of the Indian Staff Corps, in the Kuen-lun 

 plains, form the subject of a paper read by Mr. W. Botting 

 Hemsley, before the Linnasan Society, and published in the 

 Society's Journal (vol. xxx., pp. 101-140). The number of 

 novelties is not great, but about thirty per cent, only extend to 

 the Himalayas. The chief interest of the collection, however, is 

 in the nature and general distribution of the plants forming 

 this exceedingly meagre vegetation, the remains, probably, of 

 a former much richer flora. Judging from the fact that many 

 of the species are found in the most widely separated parts of 



the country, even those that are not known to occur outside of 

 Thibet, there must be very few local species. A large majority 

 of the plants scarcely lift themselves above the surface of the 

 soil, the characteristic type being a rosette of small leaves 

 closely appressed to the ground with a central sessile inflo- 

 rescence. With regard to altitude, filty-seven, or just half, of 

 Thorold's plants were collected between 17,000 and 18,000 feet, 

 five between 18,000 and 19,000, and one, Saussurea tridactyla, 

 at 19,000 feet. 



Foreign Correspondence. 



London Letter. 



ORCHIDS were the principal feature among the ex- 

 hibits at the last meeting of the Royal Horticultural 

 Society, and a lecture by Mr. G. Nicholson, Curator, Royal 

 Gardens, Kew, on hardy flowering trees and shrubs served 

 to attract a large attendance. Mr. Nicholson is the ac- 

 knowledged, authority on all matters concerning cultivated 

 trees and shrubs, his long experience at Kew T having 

 afforded him exceptional opportunities, which he has made 

 the most of. His lecture was limited to a consideration of 

 the rarer trees and shrubs which deserve to become pop- 

 ular in gardens, and which may be seen in the Kew col- 

 lection. We have had three lectures this year on much the 

 same subject, those by Mr. J. Veitch on the trees and 

 shrubs of Japan, and by Monsieur Vilmorin on the Harvard 

 Arboretum, being of the same tenor as Mr. Nicholson's. 

 The Society has urged exhibitors to send to the meetings 

 this year examples of all interesting and rare hardy trees 

 and shrubs, and as these have flowered exceptionally well, 

 some good shows have been the result. Kew has been to 

 the fore in sending specimens of the rarer hardy plants, 

 while nurserymen who are interested have contributed 

 collections comprising numerous rare and promising 

 things. The meetings of the Society are now very popu- 

 lar, being attended by many who are professionally inter- 

 ested, as well as by most of the wealthy amateurs of the 

 art of horticulture within easy reach of London. No better 

 means could be devised for the development of horticul- 

 ture than these periodical meetings, with the exhibitions of 

 all that is new and interesting among cultivated plants and 

 lectures by representative men. 



New Orchids. — No less than six first-class certificates, ten 

 botanical certificates and twelve awards of merit were 

 given by the Orchid Committee to plants shown last Tues- 

 day, evidence, if that were needed, of the extraordinary 

 amount of attention these plants continue to receive in 

 England. The most noteworthy of those certificated were 

 three hybrid Masdevallias, shown by Messrs. J. Veitch & 

 Sons: M. Asmodei, a hybrid between M. Reichenbachii 

 and M. Chelsoni, and pretty enough in the color and form 

 of its flowers to find general favor ; M. glaphyrantha, a 

 hybrid between M. Barlceana and M. infracta, with pur- 

 plish flowers, too dull, I am afraid, to please many tastes ; 

 M. Parlatoreana, a hybrid between M. Veitchii and M. Bar- 

 lceana, was raised by Messrs. Veitch and distributed by 

 them several years ago, but it had not before received a 

 certificate. Hybrid Masdevallias are now fairly numerous, 

 they are all interesting, especially to the botanist, but I 

 question if any of them is an improvement in a horticul- 

 tural sense on its parents. 



Dendrobium Guibertii. — Messrs. F. Sander & Co. showed 

 this form of D. Griffithianum. It has large golden-yellow 

 flowers, suggesting a small-bulbed form of D. densiflorum. 



Aerides maculosum Schrckderi. — This was shown by Sir 

 Trevor Lawrence, and, although not new, was considered 

 rare and distinct enough to deserve a first-class certificate. 

 It bore a four-branched spike of large lilac-rose and purple 

 flowers. 



Cattleya Mossle alba. — A very superior form of this Cat- 

 tleya was shown by Mr. H. T. Pitt, which would be C. 

 Wagneri were it not for a tinge of purple on the front lobe 

 of the labellum. 



Odontoglossum crispum. — We have already scores of 



