496 



DISEASES 



DISPORUM 



to l^e oue of this class, and is as iateres-ting to the vege- 

 table pathologist as it is destructive to the orchardist. 

 The latest view of this particular form of disorder is 

 that of the uuorganized ferment, which by causing cer- 

 tain chemical changes in the substances of the cells brings 

 about the peculiar and well marked malady of the " yel- 

 lows." If we start with the premise that there is a cer- 

 tain small amount of chemical ferment in all plants, it 

 is only necessary to have this increased to get the re- 

 sults in question; and how to prevent this augmentation 

 is the practical point at issue. This ferment in active 

 form might be communicated from one plant to another 

 by budding or grafting, and, instead of introducing liv- 

 ing germs, it is a transmission of a germless ferment 

 like diastase, that is found in seeds, and does its ap- 

 pointed work as a solvent, in the period of germination. 

 There are other disorders that are called " (Edema, " or 

 a dropsical form of disease. The tomato ia subject to 

 this, and pelargoniums likewise. Tumors are formed, or 

 the leaves bear translucent dots along the veins. This 

 trouble is most apt to appear with greenhouse plants in 

 early spring, and may be favored by lack of sun- 

 shine, especially if the warm soil is wet and root action 

 is excessive. The remedy lies in furnishing, so far as 



727, A blight of gfrapes due to some constitutional disorde 

 Notice that the leaves die first at the edges (X H). 



possible, the conditions opposite to those above named. 



In general, it may be said that diseases which are 

 due to germs or to malnutrition show the disorder 

 more or less generally spread over the plant, rather than 

 confined to local areas. For example, if the foliage 

 shows a general wilting, it is evident that the trouble 

 lies farther back than the leaves themselves. If one 

 leaf begins to die all around the edge (as in Pig. 72G), it 

 is indication that the trouble is a cutting off of food 

 supply in the entire leaf; the trouble may be near the 

 base of the leaf, or farther back. After a time, the leaf 

 becomes dry and brittle, and the winds break it. In Fig. 

 727 it is evident that the trouble is in the whole branch. 

 Byron D. Halsted. 



DISHCLOTH GOUBD. See Luffa. 



BISFORUM (Greek, douhle poretl). LiliAcew. Per- 

 ennial herbs with the appearance of our much-loved 

 eastern Bellwort or Uvularia, but distinguished by an 

 indehiscent berry, while Uvularia has a capsule that 

 splits down the back of each cell. In 1879, Bentham and 

 Hooker proposed to include Prosartes in this genus. 

 The American species of Prosartes are said by S. Watson 

 to differ from the Asian ones in having their ovules hung 

 from the top of the cell instead of ascending from the 

 base, but in one American species, Z>. trachyrarpd, they 

 are fixed on the sides, as they are also in one Himalayan 

 species. The habit of all is said to be alike. Latest 

 monograph of both genera by Baker in Journ. Linn. Soc. 

 li:586, 588 (1875) ; of the American species of Prosartes 

 by S. Watson, in Proc. Am. A^ad. 14:270 (1879). 



These plants have been little tried in the eastern 

 states, and are probably not hardy without some winter 

 covering. 



A. I/vs. rarely cordate at base: stigma S-cleft. 



B. Perianth very broad and unequally rounded at 



the base. 



M6nzieBii, Nicholson (P. Mhiziesii, Don). More or 

 less woolly-pubescent: stem 2-3 ft. long, forking, arch- 

 ing above: Ivs. ovate to ovate-lanceolate, narrowly acu- 

 minate or the lowest acute, sessile, 2-3 in. long, often 

 resin-dotted: fls. 1-3, greenish, from the topmost axils, 

 nodding, 7-9 lines long; pedicels puberulous; perianth 

 segments nearly erect, acute, 6-\l lines long; stamens 

 a third shorter ; anthers included, lK-2 times shorter 

 than the filaments; berry 3-6 seeded: cells 1-2-seeded: 

 fr. oblong-obovate, narrowed to a short beak. Calif. 

 to B. C. 

 Bij. Per i until narrow and more wedge-shaped at the base, 



lanugindsum, Nicholson. Woolly-pubescent: Ivs. ob- 

 long-lanceolate, narrowly acuminate: perianth-segments 

 greenish, linear-lanceolate, acuminate, spreading, 6 or 7 

 lines long, stamens a third shorter; style and narrow 

 ovary glabrous: capsule oblong-ovate, obtusish or with 

 a very short, stout beak, glabrous ; cells 1-2-seeded. 

 W. N. Y. to Ga. and Tenn. B.M. 1490. -Int. by H. P. 

 Kelsey. 



trachycArpum, Hook. & Jack. (P. Innhiii-iir/ni .'Wats.). 

 .Mniv or Irss j.uIh. scent: stem 1-1'. tt. lii-li. forking, 

 with fulianv "II till' upper half: Ivs. ..vatr t.. oMong-lan- 

 ceuUito, acute or rarely acuminate, 2-4 in. luny ; pedicels 

 pilose ; perianth-segments whitish, slightly spreading, 

 more narrowly oblanceolate than in />. Alenziesii, acute, 

 4-6 lines long, about as long as the stamens: berry 

 many-seeded; cells 2-6-seeded: fr. broadly obovate, ob- 

 tuse, rather deeply lobed, papillose. Saskatchewan to 

 N. Idaho, Utah and Colo. 



AA. Lvs. mostly cordate-clasping. 



Oreg&num (P. Oregdna, S. Wats.). More or less 

 woolly-pubescent: lvs. ovate to oblong-lanceolate, long- 

 acuminate: perianth segments spreading, acute, nar- 

 rowed below, very distinctly net-veined, 5-7 lines long, 

 as long as or shorter than the stamens : fr. ovate, 

 acutish, somewhat pubescent; cells 1-2-seeded. Oreg. 

 and Idaho to B. C. 



The following kinds are cult, abroad: D. Hobkeri, Nicholson 

 (P. I.inuginosa, var. Hookeri, Baker). Before D. Oreganumin 

 the key. More or less rough-pubescent, with short, usually 

 spreading hairs : lvs. ovate or sometimes oblong : perianth 

 rather broad at the base: fr. obovate. obtuse; cells usually 2- 

 Calif. Baker regards this as a more robust form of 



