First the Seed, Then the Tree 



133 



in which the seeds are placed in moist 

 sand, acid granular peat, or chopped 

 sphagnum moss and held at 32 to 41 

 F. for 1 to 4 months; and (2) chemi- 

 cal treatment, in which the seeds are 

 soaked in such materials as thiourea or 

 exposed to fumes of such substances 

 as ethylene chlorhydrin. The chemical 

 treatments have been largely confined 

 to experimental use. 



To overcome double dormancy, the 

 seed coat must be made permeable 

 and the embryo or stored food induced 

 to undergo the changes necessary for 

 germination. Sometimes cold stratifi- 

 cation is sufficient, but more often 

 soaking in hot water, acid treatment, 

 scarification followed by cold stratifi- 

 cation, or warm followed by cold strati- 

 fication is necessary. Double dormancy 

 can often be broken by sowing the 

 seed soon after collection in the late 

 summer and early fall. 



Out of 444 species of tree and shrub 

 seeds studied, 33 percent were non- 

 dormant, 7 percent had seed-coat 

 dormancy, 43 percent had internal 

 dormancy, and 17 percent had double 

 dormancy. A single species may have 

 both dormant and nondormant seeds, 

 or more than one kind of dormancy. 



Typical species with dormant seeds : 



Seed coat dormancy: Acacias, 

 amorphas, Dahurian buckthorn, felt- 

 leaf ceanothus, the hairy ceanothus, 

 Monterey ceanothus, Kentucky coffee- 

 tree, honeylocusts, black huckleberry, 

 locusts, mesquite, common persimmon, 

 silktree, western soapberry, sumacs 

 (except skunkbush) . 



Internal dormancy: Alders (except 

 European) , the ailanthus, apples, most 

 ashes, baldcypress, barberries, beeches, 

 bigcone-spruce, birches (except river) , 

 antelope bitterbrush, American bitter- 

 sweet, buckeyes (except California), 

 alder buckthorn, glossy buckthorn, 

 cascara buckthorn, buffaloberries, lilac 

 chaste-tree, cherries, American chest- 

 nut, chokeberries, creepers, currants, 

 flowered dogwood, devils-walkingstick, 

 Douglas-fir, euonymuses, filberts, firs, 

 fringetree, gooseberries (except round- 

 leaf), riverbank grape, hackberries, 



hemlocks, hickories, hollies, honey- 

 suckles, eastern hophornbeam, com- 

 mon hoptree, American hornbeam, 

 junipers, most larches, common lilac, 

 Pacific madrone, magnolias, most of 

 the maples, the European mountain- 

 ash, mountain-laurel, the mulberries, 

 bitter nightshade, black oaks, oleasters, 

 pawpaw, common pear, most pines, 

 plums, common prickly-ash, European 

 privet, sassafras, serviceberries, com- 

 mon sea-buckthorn, Fremont silktassel, 

 Carolina silverbell, common spicebush, 

 spruces (except the western white), 

 sweetgum, sycamores, common trum- 

 petcreeper, tupelos, viburnums, wal- 

 nuts, southern waxmyrtle, checker- 

 berry wintergreen, yellow-poplar. 



Double dormancy: Bristly aralia, 

 black ash, blue ash, European ash, 

 bearberry, most ceanothuses, coto- 

 neasters, most dogwoods, elders, fre- 

 montia, the panicled goldenrain-tree, 

 downy hawthorn, black jetbead, some 

 junipers, common jujube, the lindens, 

 manzanita, Amur maple, American 

 mountain-ashes, the mountain-holly, 

 Osage-orange, Digger pine, Swiss stone 

 pine, whitebark pine, raspberries, east- 

 ern redbud, meadow rose, wild-sarsa- 

 parilla, snowberries, skunkbush sumac, 

 witch-hazel, yellowwood, yews. 



SEED QUALITY largely governs the 

 rate at which seeds should be sown to 

 produce a certain number of good 

 seedlings. Tests can disclose several of 

 the fundamental characteristics of qual- 

 ity: Genuineness, purity, number of 

 seeds to the pound, moisture content, 

 and viability. 



The sample tested should be truly 

 representative of the entire lot. Repre- 

 sentative sampling can be attained 

 either by thorough mixing of the en- 

 tire seed lot before sampling, or by 

 drawing a number of small subsamples 

 of equal size at random from different 

 parts of the lot in proportion to the 

 quantity of seeds in each part. The 

 number of seeds required for a germi- 

 nation test seldom should be less than 

 400, tested separately in four equal 

 parts. For lots larger than 100 pounds, 



