THALAMIFLORZ 33 
is in concentric rings, a ring denoting a year’s 
growth. 
The leaves in this group have the nerves also 
arranged in a network, or branched. 
The flowers have the parts usually in fours or 
fives. Annuals and biennials do not have the same 
stem structure as perennials. There are exceptions 
to these definitions, as, for instance, the Ranuncu- 
laceous Evanthis has but one cotyledon, and some 
monocotyledons have the leaves net-veined, as 
Arum. 
Dicotyledons are divided into four groups accord- 
ing to the character of the perianth. Thus in Mono- 
chlamydez or Apetale it is single or absent. In the 
three groups Corolliflore, Thalamiflore, and Calyci- 
flore it is double. 
In Corollifloree or Gamopetalz petals are united. 
In Thalamiflore and Calyciflore or Polypetalz 
the petals are distinct, the former having the stamens 
hypogynous or situated below the ovary, the latter 
perigynous, or around the ovary, or epigynous, or 
upon the ovary. 
Amongst Polypetalz which possess both calyx and 
corolla (or Dichlamydez) with petals distinct there 
are some exceptions; thus in Ranunculacez, Meadow 
Rue has no petals, nor has Anemone, the sepals 
being petaloid, and there are no petals in Marsh 
Marigold, and amongst Crucifers, Cardamine, Wart 
Cress, Pepperwort are wanting in calyx or corolla, 
whilst there are apetalous forms of Violet, and 
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