66 
THE INFLORESCENCE 
flowers. Thus the umbels of Xanthosia and Chorizanthe, 
the dichasia of Mirabilis, the heads of Echinops, are each 
one-flowered ; the female head of Xanthium two-flowered. 
In these cases comparison with the related forms, and the 
frequent possession of an involucre by the one flower, leaves 
no doubt as to the explanation. An immense number of 
plants have true solitary flowers, i.e. usually one flower in 
each leaf-axil, loosely arranged on the main axis. These 
may be reduced inflorescences, but in most cases, probably, 
are not so. 
One of the most interesting cases of reduction is the cyathium of 
Euphorbia (q.v.), in which a whole inflorescence is reduced in such 
a way as to look like a single flower, whilst really composed of many 
individual flowers. This inflorescence has separate male and female 
flowers, arranged in a definite way with regard to one another ; similar 
phenomena occur in many Moraceae ( e.g . Brosimum), Begonia, Echino- 
phora, Ficus, Cyclanthus, &c. All these have inflorescences of peculiar 
types; cf. Part II. for details; see also Urticaceae, Triumfetta, Spiran- 
thes, Acroglochin, Rhus, &c. 
One advantage, underlying the differentiation of the 
shoot into vegetative and reproductive parts, seems to be 
the formation of many spores near together on the shoot. 
In Cryptogams this is useful because the prothalli will tend 
to be nearer together upon the soil, thus favouring fertilisa- 
tion. In flowering plants the microspores (pollen) have to 
be carried to the ovules or carpels, generally by the aid of 
wind or insects. The massing together of the flowers tends 
to free them from the vegetative leaves, which interfere with 
wind-transport by interposing obstacles, and with insect- 
transport by rendering the flowers less conspicuous. The 
more the flowers are massed together the more conspicuous 
do they become, the more quickly can they be visited by 
insects, and the smaller the size of the individual flower 
may be. The highest degree of perfection in this way is 
found in the Compositae (q.v.). Conspicuousness is often 
gained in other ways, e.g. by ray flowers, as in Compositae, 
&c., coloured bracts (see above), unilateral arrangement of 
the flowers (Digitalis, Mitella, Boraginaceae, &c.), and so on. 
The Flower may be defined as a reproductive short 
shoot. It consists essentially of an axis ( receptacle , thalamus , 
or torus) bearing sporophylls ( stamens and carpels). These 
are the essential organs , and there are usually also some 
