CONIFERiE. 



SILVA OF NORTH AMERICA. 



61 



genus probably once occupied a more important position in northern forests, for traces of what are 



believed to be extinct species have been found in the Jurassic rocks of Spitzenberg, northern Europe, 

 and Siberia.^ 



The bark of Tsuga is rich in tannin, and that of the American species is largely used in tanning 



leather, and occasionally in medicine. As a timber-tree the most valuable of the genus is Tsuga 



heterophylla of the northwest coast region of North America. 



Tsuga is not injured by the attacks of many insects^ or by numerous fungal diseases.' 



All the species are cultivated for the decoration of parks and gardens, and no other conifers 



surpass the Hemlocks in grace and beauty. They can be easily raised from seeds, although the young 



plants grow slowly. 



Tsuga, the Japanese name of the Hemlock-tree, was first used by Endlicher* to designate a 

 section in his genus Pinus, and afterward by Carriere, who separated the Hemlocks into a generic 



group, as the name of his genus. 



bert, Pinus, ed, minor, ii. 80, t. 46. — Parlatore, De Candolle 

 Prodr. xvi. pt. ii. 429. 



Pinus Brunoniana, Wallicli, PI. Asiat Rar. iii. 24, t. 247 

 (1832). — Antoine, Conif. 82, t. 32, f, 1. — Endlicher, Syn. Conif. 

 84. — W. E. M'Kab, Proc. R. Irish Acad. ser. 2, ii. 213, t. 23, 

 f . 5. 



AUes Brunoniana, Lindley, Penny Cycl. i. 30, f. (1833). — 

 Madden, Jour. Agric. and Hort. Soc. Ind. iv. pt. iv. 95 (Hima" 

 lay an Conif erce). — Gordon, PinetuTUj 13. 



Abies dumosa, Loudon, Arh. Brit. iv. 2325, i. 2233, 2234 

 (1838). — K. Koch, Dendr. ii. pt. ii. 252. 



Abies species, Griffith, It. Not. ii. 141 (1848) ; Icon. PI Asiat. 

 iv. t. 375 (Taxi on plate). 



Tsuga Brunoniana, Carriere, Traite Conif, 188 (1855). — Mas- 

 ters, Gard. Chron. n. ser. xxvi. 500, f. 101. — Hooker f. Fl. Brit. 

 Ind, V. 654. — Beissner, Handh, Nadelh. 397. 



Picea {Tsuga) Brunoniana, Bertrand, Ann. Sci. Nat. sdr. 5, 

 xs. 89 (1874). 



Tsuga dumosa is distributed over the inner ranges of the Hima- 

 layas from Kumaon to Bhotan, at elevations of between eight 

 thousand and ten thousand five hundred feet above the level of 

 the sea, in Sikkim forming great forests with AUes Wehbiana. It 

 is a stately pyramidal tree, sometimes one hundred and twenty-five 

 feet in height, with a trunk eight or nine feet in diameter, spread- 

 ing branches, pendulous bri^aehlets, and erect or horizontal cones. 

 (See Hooker f. Bimalayan Journals, n. ed. ii. 121 ; Gard. Chron. 

 n. ser. xxvi. 72, f. 14.) The wood is white, tinged with pink, soft, 

 and not durable; in Sikkim it is made into shingles, and the thick 

 rough bark is employed for roofing (Brandis, Forest Fl. Brit. 

 Ind, 527. — Gamble, Man. Indian Timbers^ 408). 



In Europe, where it was introduced sixty years ago, the Hima- 

 layan Hemlock has not proved very hardy, and usually suffers 

 severely from late spring frosts, although it has produced cones 

 in a few sheltered positions in southern England. (See Fowler, 

 Gard. Chron. 1872, 75.) It has not yet shown itself able to with- 

 stand the climate of the United States. 



^ Saporta, Origine Paleontologique des Arbres, 14:. 



2 The Hemlock-trees of eastern North America appear to be 

 peculiarly exempt from attacks by boring insects in the living 

 stems, and nothing practically is known of parasites on the two 

 species which inhabit the northwestern part of the continent. The 



insects found in the trunks of Hemlocks are usually borers, which 

 prey only upon dead or dying wood, and do not affect living trees. 

 These insects are also found on the allied genera of conifers. 



Various species of leaf-eating insects occasionally feed upon the 

 foliage of Tsuga, but few of them are sufficiently abundant to 

 attract attention. The larvse of a Tineid, GelecUa abietisella, 

 Packard, cut off small groups of Hemlock leaves, fasten them 

 together by silken threads, and, living within the protecting case 

 thus formed, devour the parenchyma of adjacent leaves. 



A scale-insect, Aspidiotus Ahietis, Comstock, is sometimes found 

 in abundance on the lower surface of the leaves of Tsuga Cana- 

 densis. 



3 Tsuga Canadensis is attacked by a number of interesting fungi 

 peculiar to this host, besides several others found also on other 

 related genera. Among the former is the rust, Peridermium PecJcii, 

 Thuemcn. This secidium, or cluster-cup, is found in summer on 

 the under side of the leaves, and resembles Peridermium columnare, 

 Albertini & Schweinitz, of Europe, which infests the leaves of Abies 

 Picea, and is connected with Calyptospora Gceppertiana, Kuehn, on 

 species of Vaccinium. Peridermium Peckii appears to be a distinct 

 species, although it is not known with what teleutosporic form it is 

 connected. Two other rusts have been observed on the leaves of 

 Tsuga Canadensis in Massachusetts (see Farlow, Proc. Am. Acad. 

 XX. 322), one of them appearing to be the same as Chrysomyxa 

 Ahieiis, Eees, which infests Picea Abies in Europe, and the other, 

 Cmorna Abietis-Canadensis, Farlow, which is related to Coeorna 

 Abieiis-pectinatce, Kees. A disease of the leaves of Tsuga Cana- 

 densis appears to be due to the attacks of Propolidium TsugcB, Sac- 

 cardo, a small dark brown Discomycete which is developed on the 

 under side of the leaves, and causes them to fall in large numbers. 



Tsuga Canadensis is subject also to the attacks of a few other 

 species of Ascomycetes, and of a considerable number of Poly- 

 poreacese, mostly not confined to this host. Polyporus Pilotce, 

 Schweinitz, infests Tsuga Canadensis on the mountains of the mid- 

 dle states. 



Three species of fungi have been reported as infesting Tsuga 

 Mertensiana, Anthostemella brachystoma, Ellis & Everhardt, Lasio- 

 sphmria stuppea, Ellis & Everhardt, and Blitrydium signatum, Sae- 

 cardo. 



* Syn. Conif. 83 (1847).' 



