514 



PART IV. CLASSIFICATION. 



SUB-CLASS I. MONOCHLAMYDE.E. 



The flowers have a simple, usually sepaloid, perianth, or it may 

 be absent ; they are commonly unisexual. 



Cohort I. Urticales. Flowers usually diclinous, in inflor- 

 escences of various forms : perianth usually present, simple, 

 sepaloid, consisting typically of five (-) or reduced to four (2 +. 2) 

 segments ; stamens equal in number and opposite to the segments 

 of the perianth, in consequence, apparently, of the essentially 

 spiral arrangement of the floral organs (see p. 446) ; ovary 

 superior, monomerous, unilocular, or sometimes dimerous with 

 two styles, and then rarely bilocular: ovule solitary, in different 

 positions. Seed commonly containing endosperm. The inflor- 

 escences in orders 1-3 are usually situated two together at the base 

 of a leafy dwarf-shoot which springs from the axil of a leaf, and 

 they are cymose (Fig. 322). The leaves are generally hirsute. 

 Cystoliths (p. 78) are commonly present. 



FIG. 322. Part of the stem of Urtica 

 urem, with a leaf (/) in the axil of which 

 is the branch (m), at the base of which 

 are the inflorescences (b), without any 

 bracts (nat. size). 



FIG. 323. .4 staminal rf ; B carpellary 

 $ flowers of the Stinging Nettle, Urtica : 

 p perianth ; a stamen ; n' rudimentary 

 ovary of the <J flower ; ap outer ; i;> 

 inner whorl of the perianth ; n stigma of 

 the $ flower (mag.). 



Order 1. URTICACELE. Ovary monomerous: ovule central, ortho- 

 tropous. Seed containing endosperm. They are mostly herbs or 

 shrubs without milky juice and frequently provided with stinging 

 hairs : leaves alternate, stipulate. Flowers polygamous, monoecious, 

 or dioecious, in paniculate or glomerulate inflorescences. 



Urtica urens and dioica (Stinging Nettles) are known by the stinging 

 hairs which are distributed over their whole surface: perianth 2 + 2; the 

 two outer segments of the perianth of the $ flower are larger than the 

 inner segments (Fig. 323 B). In the former species the $ and ? flowers 

 are contained in the same panicle, and the floral axis is but feebly de- 

 veloped ; in the latter they are on different plants, and the axis is well 



