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 (1—2 in.) spirally arranged on erect 

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

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

 season, few. wiihout 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 i (-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 difi"erentiated, 6 mm., stony sclerotesta; endosperm with 

 fat-storage ; embryo small, 2 cots. 



IVo^e : slow growth and great shade-endurance ; spiral bud-galls by omission of 

 internodal extension and D.V. mechanism {Ceddomyia 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. (= Salisbtirm adiantifoh'a. 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 sHght 

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

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

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

 cambium suppressed. 



Nole 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, 

 I 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 i (-2) ovules, borne on long stalk (i 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 i 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. 



Nole 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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