INTRODUCTION 
stamens and carpels are present in the same flower, it is perfect ; if only one 
class of these essential organs is present, the flower is imperfect , and staminate 
or carpel late, as the case may be. Plants with imperfect flowers may be 
either monoecious (Greek /xoi'os, monos , one ; ol *05, oikos, a house), where, 
as in the Scots Pine and the Oak, staminate and carpellate flowers occur on 
the same plant ; or dioecious (Greek St, di-, two), where they are on distinct 
individuals, as in the Willows and Poplars. In the few cases in which 
neither stamens nor carpels are present, as in the outer florets of the blue 
Cornflower, or the outer flowers in the cluster of the Guelder-Rose, the 
flower is termed neuter. In a wild state, all the flowers of a plant are 
probably never neuter ; but they are so in the Snowball-tree, a cultivated 
form of the Guelder-Rose. 
Some plants, in addition to their more conspicuous flowers, produce, 
generally later in the season, others which never open, but, though remaining 
bud-like, produce abundant fertile seed. Such flowers occur in the Sweet 
Violet and Wood-sorrel, and are known as cleistogene (Greek K-Xacrro?, 
kleistos, closed ; yeVo?, genos, birth). 
In perfect flowers the stamens and carpels may reach maturity simul- 
taneously, that is to say, the stamens may be ready to burst and discharge 
their pollen whilst the carpels are in a receptive condition, so that self- 
pollination is at least possible. This is commonly the case in small incon- 
spicuous flowers and is termed homogamy (Greek o/xos, homos , alike ; yd/xos, 
gamos, marriage). In other cases the stamens and carpels mature at 
different times, or are dichogamous (Greek dichos , apart) : — either, as is 
more commonly the case, the stamens maturing before the carpels, when 
the flower is called protandrous (Greek 7rpwros, protos , first ; avSpbs, andros , 
of a man) ; or the carpels before the stamens. This latter is termed 
protogyny (Greek v pcbrcy;, protos, first ; ywrj, gune, a woman), and, for some 
unexplained reason, occurs generally in plants in which the pollen is carried 
from plant to plant by wind, as in the Plantains. If plants are completely 
dichogamous it is obvious that they cannot be self-pollinating. 
In what appear to be primitive types of flower, as in the little Mouse- 
tail ( Myosurus ), a member of the Buttercup Family, the floral receptacle is 
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