September i, 1897.] 



Garden and Forest. 



34i 



comparatively clear. We can easily believe that there 

 have been numerous independent hybrid origins followed 

 by still more numerous secondary, tertiary and quartenary 

 crosses, and these would account fully for the extraordinary 

 variability and wide diversity of characters among these 

 Plums. The varieties of the Miner group may reasonably 

 be supposed to be secondary hybrids between Wild Goose 

 types and Prunus Americana ; or they may be, in some 

 instances, primary hybrids in which the Americana influ- 

 ence has preponderated. Such varieties as Ohio Prolific, 

 Schley, Texas Belle and Wooten may be supposed, on the 

 other hand, to be secondary hybrids between Wild Goose 

 and the Chicasaws. 



All this will drive every Plum student, pomologist or 

 botanist to a conclusion which we ought to have reached 

 independently before, namely, that no full classification of 

 our cultivated varieties can be made which shall be satis- 

 factory to everybody. It is a matter of unquestionable 

 convenience to divide our multiform varieties into several 

 groups, but the lines between these groups are purely 

 imaginary and arbitrary, and certain varieties which come 

 near the division-line somewhere may be put into one 

 group by one man and into the other group by another, 

 and both men be right. It is all a matter of judgment, and 

 a very delicate matter, too. There has already been too 

 much controversy over some of these doubtful varieties. 

 What plum students need now is less controversy and 

 more patience. 



The cultivated Hortulana Plums may be best understood 

 by arranging them in four groups. Three of these have 

 been mentioned — the Miner group, the Wild Goose group 

 and the Schley or Clifford group. These form an unbroken 

 series from Prunus Americana to P. angustifolia. There is 

 a fourth group at present classified with the Hortulanas, 

 but comparatively distinct from the others. This group is 

 made up of such varieties as Wayland, Moreman, Golden 

 Beauty, Reed, Leptune, Kanawha and others. I may be 

 able to add a word concerning this group at another time. 



Universily of Vermont. F. A. Waitgll. 



Cruelty of Asclepias. 



THE Butterfly Weed, Asclepias tuberosa, is one of 

 the most conspicuous plants in the Pines, and the 

 flowers are seen all summer long on the different plants 

 which peep out from under hedges and other shady places. 

 The flowers vary in color from the deepest orange-red to 

 pale yellow, and unlike the other species this plant has no 

 milky juice. Another common species, A. obtusifolia, is 

 quite different from A. tuberosa in its power to capture and 

 hold insects until they die. Some of the other species have 

 the same power in a more limited degree, but A. obtusi- 

 folia is by far the most cruel member of the family. The 

 hoods surrounding the stigma which contain the nectar are 

 comparatively short in this species, so that insects probing 

 for the nectar often make a mistake and strike the cloven 

 gland from which the pair of pollen-masses are suspended. 

 Honeybees are the most common victims, and sometimes 

 they are caught by the feet and sometimes by the probos- 

 cis. When caught by a foot in its struggles to free itself 

 it often strikes another gland on the same or on an adjacent 

 flower, when its frantic efforts increase until each foot is 

 held as in a vise. The gland seems to be sensitive and to 

 close more firmly about its victim the more it struggles, 

 but if this is true it does not relax its hold after the insect 

 is dead, as sensitive glands usually do. It requires careful 

 work to extricate the insect in order to find just how it is 

 caught. The pollen-masses are something like an old- 

 fashioned pair of saddle-bags and hang by black-looking 

 threads joined together at the summit, where it is attached 

 to the gland which holds the insect. On loosening and 

 pulling out this gland it brings with it the curious pollen- 

 masses, and the foot or tongue of the insect is always 

 found fast in the opening or slit of the gland, which seems 

 to have closed around it. It has Ions: been known that 



the pollen-masses were liberated by the agency of insects, 

 but why so many should be held prisoners and tortured in 

 this cruel manner is one of the mysteries of plant-life. Not 

 only bees but many small handsome butterflies are caught 

 by the tongue and held until they die, and sometimes, but 

 much more rarely, large beetles are caught. In one 

 instance I found the large white-lined Saperda, the parent 

 of the Apple-tree borer, held by three different flowers, and 

 strong as this beetle is it was unable to free itself and so 

 died. It is not at all uncommon to find Rose-bugs made 

 prisoners. 



The Swamp Milkweed, Asclepias incarnata, has this 

 power to a certain extent. A few days ago several stems 

 of this plant, with their numerous umbels of small pinkish 

 flowers, were brought from the woods for class purposes 

 and set on the porch in a jar of water. I soon noticed a 

 strange fly flitting about them, the size of the common 

 house-fly, but with a proboscis which could probe to the 

 bottom of the hoods so as to reach the honey. It was 

 probably some species of Chrysops, as it closely resembled 

 the Golden-eyed Chrysops which sometimes so persistently 

 flies about our heads in its effort to bite. But this species, 

 although it had a wicked-looking proboscis, never at- 

 tempted to bite, and its sole business was with the flowers. 

 A score or more were about the plant, jostling each other 

 in their eagerness for the unrifled flowers, so it seems that 

 this fly is the main instrument in perpetuating this species 

 of Asclepias. Occasionally a fly was caught by a foot and 

 held for a moment, but usually it escaped, and it had done 

 the work of extricating the pollen-masses from the cells so 

 the stigma could be reached. 



I have not studied this plant in its home in the swamp, 

 but here on the porch this fly was the only visitor. I placed 

 a jar of Asclepias tuberosa by the side of A. incarnata, and 

 soon several butterflies and other insects alighted on the 

 former, while they passed the latter by, or merely hovered 

 over it for a moment without alighting. A fine Danais 

 butterfly came and sipped the nectar from A. tuberosa, 

 scarcely deigning to notice A. incarnata, and yet she must 

 have alighted on the plant in its home long enough 

 to leave her eggs, for two of her baby caterpillars were 

 feeding on the stems. It is remarkable that this but- 

 terfly recognizes all the species of Asclepias and makes 

 use of them as food-plants for her children ; for exam- 

 ple, in appearance and in texture of the stems and 

 leaves A. tuberosa is totally unlike A. obtusifolia. The two 

 species seem to have nothing in common except the flowers 

 and seeds. A. tuberosa has small green leaves without 

 milky juice, while A. incarnata has a copious supply of the 

 milky fluid, and yet before they bloom our butterfly knows 

 the plants and uses them as food for her young. 



As butterflies and wasps passed A. incarnata by, so the 

 fly paid no attention to A. tuberosa. It knew without mak- 

 ing the attempt that it could never reach the nectar at the 

 bottom of the long hoods of this species. In my limited 

 study of the Swamp Milkweed I did not find but one fly 

 that it had killed and this was held by one foot. On extri- 

 cating it I found the foot fast in the gland in the same way 



that A. obtusifolia holds its victims. , r „ 



Vineiand, N. J. Alary Ireal. 



Notes from Santa Monica Forestry Station. 



CONSPICUOUS among summer-flowering Eucalypti 

 growing here are the following : 

 Eucalyptus citriodora, or more correctly, E. maculata, 

 var. citriodora (F. von Mueller), the lemon-scented Gum- 

 tree. This is an erect, straight-stemmed tree, of rather 

 slender and decidedly elegant habit, sparingly branched, 

 but with numerous long, drooping branchlets, often over ten 

 feet in length. The leaves are long and narrow — lanceo- 

 late-falcate in shape, nine to twelve inches long, and one 

 inch broad at the widest part, tapering gradually to a blunt 

 point. They are bright green on both sides, with a conspicu- 

 ous midrib, yellowish green in the older leaves, maroon in 

 the young foliage. The petioles and young branchlets are 



