Gymnospermae Coniferae Taxoideae Taxineae. XIV. 



TAXUS (in possibly 7 geograpical races). Isolated type of N. Temp. 

 Forest-tree with general Conifer-habit, but no cones ; ovules solitary, with succulent 

 seed investment (' aril ') ; dispersed by bird-agency. 



Type Taxus baccata, Yew, 80 ft., and diam. to 6 ft., age to 1500 (B.G.O., 

 30 ft. and 300 years). Indig., Central and S. Europe to Himalaya. Growth slow. 



Annual shoot ; leaves as flat needles (12 in.) spirally arranged on erect 

 shoots (cf. fasiigiate form, ' Irish Yew '), dorsiventrally pectinated in 2 rows on 

 laterals. No other D.V. shoot-construction ; laterals in axils of leaves of previous 

 season, few, without rule, freely produced when shoots are cut back, hence use in 

 topiary work. Dioecious (with rare monoecism). 



Staminate flowers similarly in axils of previous season, without rule, abundant, 

 turned to lower surface below needles; 10 mm., perianth of distinct scales, larger 

 upward, 2 last often prominent (5 as full cycle) ; distinct floral internode (3 mm.), 

 stamens few (15-16), as peltate sporophylls with 5-9 pollen-sacs; pollen small round, 

 25 fx', with ' smoke-effect' as light grains rise in air. Pollination Jan., Feb. 



Ovulate flower a reduction-limit; special short shoots of spirally arranged 

 scales (8-13), 2 mm. over all, similarly borne in leaf-axils and deflected to lower side ; 

 each bears 1 (-2) lateral axes of a few (6) scales enclosing a terminal ovule, the latter 

 taking the end-position, with exposed micropyle only, and conspicuous drop-mechan- 

 ism. Wind-pollination effective ; ovules enlarge to green ' berry ' structures, enclosed 

 in secondary growth of a green collar-investment (= 'aril'), with special protective 

 function (summer), dilating and ripening Sept. 



Adult seed, ovoid, 10 mm. by 8, included in bell-shaped aril, enlarged and 

 dilating at end, bright red, succulent, sugar-storing ; pigments anthocyan and residual 

 carotin (cf. yellow-fruited var.). Taken freely by thrushes, &c, in Nov. (usually all 

 stripped by Dec). Testa differentiated, 6 mm., stony sclerotesta ; endosperm with 

 fat-storage ; embryo small, 2 cots. 



Note : slow growth and great shade-endurance ; spiral bud-galls by omission of 

 internodal extension and D.V. mechanism (Cecidomyta Taxi) ; Fastigiate var. also 

 with omission of D.V. organization, (Irish Yew) carpellary sport, but others staminate. 



GINKGO B I LOB A, important monotype, as representative of oldest series: 

 100 ft., China, Japan, and in cult. (= Salisburia adiantifotia, Maidenhair tree): com- 

 bines distinct factors as a unique survival ; fertilization (Cycad), stem (Conifer), fruit 

 (Taxoid), foliage (Fern). The only tree with motile male gametes. 



Annual shoot ; leaves spirally arranged, broad (2-3 in.), petiolate (2-3 in.), 

 wedge-shaped or 2-lobed, with dichotomous venation, deciduous; T-bud with slight 

 crater ; developing leaves and all tissues with excess cluster-crystals of calc. oxalate ; 

 spurs on second-year shoot in manner of Lartx, functional for 10 years, 1 in. long, 

 rarely branching or becoming leaders; crown of leaves (3-5) each season, and 

 cambium suppressed. 



Note bud-scales and leaf-scars, internodes extended 1-2 in.; no D.V. habit, 

 laterals ascending at wide angles. Dioecious (rarely flowering in Britain). 



Staminate flower; several (3-5) on spur-shoot before the leaves are grown, 

 1 in. long; stamens about 50, pollen-sacs 2, pendulous (2 mm.). Pollen, 30 /a, 

 spherical, not winged. Pollination in April, output enormous. 



Ovulate flower, of 1 (-2) ovules, borne on long stalk (1 in.), 1-8 on a spur with 

 the young foliage ; ovule 2 mm., with basal ' collar '-rudiment ; growing to a large 

 ' berry '-structure, size of small green plum ; fertilization late in Sept., Zoi'dogamic ; 

 antherozoids 2 from { pollen tube ', motile, multiciliated, 100 /x long, free-swimming 

 in pollenic-chamber of nucellus, with 'tent-pole' mechanism. 



Ripe ovule over 1 in., ripened same season (Nov.), appearance of yellow plum ; 

 sarcotesta yellow, succulent ; sclerotesta of stone-cells as ' plum-stone '. Embryo 

 with 2 cots., endosperm storing starch ; germination hypogeal type ; first leaves 

 scale-like, a few normal leaves and terminal bud only as the first season's growth. 



Note lack of excessive xerophytic adaptations, beyond deciduous habit ; extreme 

 reduction of ovulate scheme, parallel with Taxus only in subsequent developments of 

 ovule in correlation with dispersal by birds. 



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