ZOSTERA 
615 
tamineae by Warming; Benth. -Hooker unite all the orders — Z., 
Musaceae, Cannaceae, and Marantaceae — into one order under the 
name of Scitamineae. 
Zinnia Linn. Compositae (v). 12 sp. N. Am., favourite border plants. 
Leaves opp. or whorled. Fruit winged. 
Zizania Gronov. ex Linn. Gramineae (vi). 2 sp. Am., N.E. As., 
Z. aquatica L. ( Hydropyrum esculentum Link), Canada rice, is used 
as a cereal by the N. Am. Indians. 
Ziziphora Linn. Labiatae (vi. 8). 12 sp. Medit., Asia. 
Zizyphus Tourn. ex Linn. Rhamnaceae. 40 sp. Indo-mal., trop. Am., 
Afr., Austr., Medit. The stipules are often represented by thorns, 
one of which is sometimes recurved whilst the other is straight (cf. 
Paliurus) ; occasionally only one is developed. Z. chloroxylon Oliv. 
(cogwood ; Jamaica) yields a hard tough wood, used for cogs in 
machinery. The fruits of many sp. are edible ; those of Z . Lotus 
Lam. (Medit.) are said to be the Lotus fruits of antiquity ; those of 
Z. vulgaris Lam. (Orient &c.) are known as French jujubes ; those of 
Z. Joazeiro Mart, are used in Brazil as fodder for cattle during the 
dry season. Z. Spina-Christi Willd. is said to have furnished the 
crown of thorns (cf. Paliurus). 
Zostera Linn. Potamogetonaceae. 5 sp. temp., subarct., subtrop., 
growing in salt water on gently sloping shores (p. 187). Z. marina L. 
and Z. nana Roth in Brit, (eel-grass or grass-wrack). The lower part 
of the stem creeps, rooting as it advances along the ground, and has 
ordinary monopodial branching ; the branches grow upwards into the 
water and exhibit sympodial branching, complicated by union of the 
axillary shoot to the main shoot for some distance above its point of 
origin. This is most easily seen in the infl. region ; the branching is 
that of a rhipidium (p. 65), but the shoot II, which springs from the 
axil of a leaf on shoot 1, is adnate to 1 up to the point at which the 
first leaf is borne on 11 ; this leaf occupies the angle between the two 
shoots where they separate. Shoot I (and 11, 111, &c. successively) is 
pushed aside and bears an infl. (See Eichler’s Bliithendiag . or Nat. 
Pfl. for details and figs.) The leaves are long, linear, and sheathing 
at the base. 
The infl. is a flattened spadix, enclosed at flowering time in a 
spathe (the sheath of the uppermost leaf). This is open down one 
side, and on the corresponding side of the spadix the flrs. are borne, 
the essential organs forming two vertical rows, each composed of a 
cpl. and a sta. alternately. On the outer side of the spadix next the 
cpl. is often a small leaf (the retinaculum of 
systematic works). The midrib of the cpl. ret * cpl * sta * 
faces outwards. Each cpl. contains one ovule ret sta* ^ 
and has two flat stigmas. The sta. consists of 
two half anthers, joined by a small connective. It is difficult to 
decide what is the actual ‘ flower ’ in this plant ; the usual view is that 
