DICOTYLEDONES : POLYPETALJJ : THALAMIFLORJ!. 



597 



one bundle. Ovary monomerous, with one basal anatropous 

 ovule : fruit a fleshy two-valved capsule : seed with ruminated 

 endosperm. 



Myristica moschata, the Nutmeg, is a native of New Guinea. The seed is 

 invested by an aril (see p. 459), an integument which is developed after 

 fertilisation ; it has a netted or laciniate appearance (Fig. 401 a) ; it is known 

 in commerce as Mace. Seed large, with abundant ruminated endosperm ; the 

 innermost layer of the brown testa closely follows all the windings, and this 

 gives the endosperm a marbled appearance. 



The affinities of this order are doubtful : it is commonly regarded as closely 

 allied to the Lauraceae. 



Order 5. POLYGON- 

 ACE^. Flowers ambi- 

 sporangiate, sometimes 

 monosporangiate by 

 suppression, trimerous 

 (sometimes dimerous), 

 with the typical formula 

 K3, 03, ^3 + 3, (9(3): 

 perianth in two whorls, 

 homochlamydeous, either 

 sepaloid or petaloid, 

 sometimes reduced to 5 

 leaves : stamens in us- 

 ually two regularly al- 

 ternating whorls ; the 

 number of stamens in 

 the outer whorl is fre- 

 quently increased by 

 duplication ; the number 

 of the stamens is fre- 

 quently reduced by sup- 

 pression. Ovary usually trimerous, nnilocular, with a single basal 

 orthotropous ovule. The fruit is more or less enveloped by the 

 persistent perianth (Fig. 402 0). The seed contains endosperm, 

 in which the straight or curved embryo is imbedded. The leaves 

 have sheathing bases, and connate stipules (Fig. 402 A), forming 

 an ocrea (see p. 48) which embraces the stem for some distance 

 above the leaf-sheath (absent in Eriogonum). 



This order, like the Lauraceae, is commonly placed in the Monochlamydeae, 

 and the interpretation of the two-whorled perianth preseats the same difficulty 



FIG. 402. A Portion of the stem (s) of Polygonum, 

 with a leaf (b), its sheath (v), and the ocrea (o) (nat. 

 size). S Flower of Rheum : fc external, c internal 

 perianth-whorl ; a the stamens. C Fruit of Rumex, 

 enclosed by the inner whorl of the perianth c ; s dorsal 

 ridge of one of the perianth-leaves ; Is external peri- 

 anth-leaves. D fruit of Rheum (/) : fc outer, c inner 

 perianth-whorl (enlarged). 



