PART III. | THE MECHANISMS OF FLOWERS. 463 
their absence fertilises itself regularly, and the other is abundantly 
visited by insects and is incapable of self-fertilisation. In Huphrasia 
officinalis and Rhinanthus crista-galli it is the small-flowered form, 
in Odontites serotina it is the plants inhabiting shady places, which 
receive so few insect-visits that self-fertilisation becomes necessary ; 
in Melampyrum and Odontites lutea self-fertilisation occurs in 
absence of insects, but in all flowers without distinction; in 
Pedicularis silvatica alone, the conspicuousness of the flowers and 
the perfection of the pollen-apparatus insures cross-fertilisation so 
well that self-fertilisation never takes place. 
The section of the Scrophularineze characterised by a pollen- 
distributing mechanism is remarkable also for the gradations in the 
development of its -nectaries. Usually part of an organ already 
present secretes honey, especially the lower part of the outer wall of 
the ovary, which sometimes secretes its honey all round (Zozzia), 
sometimes mainly or solely in front (Huphrasia and Odontites). 
With the growth of this new function the secreting tissue 
thickens and forms a protuberance scarcely noticeable in Huphrasia 
minima, but evident in #. salisburgensis and Pedicularis aspleni- 
folia, Fl.; it becomes a strongly marked swelling in P. verticillata, 
L., and P. recutita, L., which in P. palustris, L., is more sharply 
marked off from the ovary, and in Rhinanthus becomes a cup 
extending forwards from the base of the ovary, which contains 
the nectar, and is most perfectly developed in &. alpinus. We 
thus have a complete series of transitions, from secretion of honey 
by an organ whose proper function is quite different, to the 
development of a special nectary. 
REVIEW OF THE SCROPHULARINE, 
The Scrophularinez described above may be arranged in four 
groups according to their pollen-distributing mechanism and the 
insects which fertilise them. 
1. Verbascum and Veronica have open flowers, with short tubes 
and freely exposed reproductive organs which insect-visitors may 
come in contact with at any part, though they as a rule touch the 
stigma before the anthers. Only in some Veronicas, especially in 
V. Chameedrys, the filaments by spreading apart and thinning away 
