TROPOPHYTES 59 
2. A few prickly, succulent, or woolly-leaved deciduous 
perennials—e.g., sea-samphire (Crithmum maritimum), sea- 
holly (Eryngium maritimum, sometimes an annual), etc. 
In nature, of course, these groups are not sharply 
separated. The divisions, being based upon the water- 
supply available during summer, must merge insensibly 
one into the other. Almost any actual plant will, owing 
to a mixture of characters, occupy a position between the 
divisions. As the environment becomes drier, the xero- 
phytic characters of the plants become more pronounced, 
while if the conditions become moister, hygrophytic 
characters will begin to dominate. 
Annuals.—We have here regarded the annual as a tro- 
pophyte, although at the end of summer the whole plant 
dies, leaving only the living seeds to carry on the race 
during the winter. Biologically, they are tropophytes, 
for it is the race that matters, not the individual. The 
seed is, of all resting forms, the most xerophytic. It can 
endure, without injury, a greater degree of drought or 
cold than any other hibernating structure. In an annual 
the summer plant is only one phase ; the young plantlet 
embedded in the seed during the winter is the other. The 
nature of the water-supply determines the characters of 
the adult, as it does those of all tropophytes. 
1. Hygrophytic Annuals.—These are few, most plants 
living in moist conditions being perennial. The following 
marsh-plants are annuals: The celery-leaved buttercup 
(Ranunculus sceleratus), marsh louse-wort (Pedicularis 
palustris), the bur-marigolds (Bidens cernua and B. tri- 
partita), and the toad-rush (Juncus bufonius). 
2. Xerophytic Annuals.—A large number of annuals 
exhibit characters which are more or less xerophytic. 
This is not surprising when we remember that annuals 
are most common in dry, waste places. 
(a) Seaside- Annuals, generally succulent: glasswort 
(Salicornia herbacea), sea-rocket (Cakile maritima), salt- 
wort (Salsola Kali), and sea-blite (Sueda maritima). 
On sand-dunes the summer is the most unfavourable 
season. Many of the annuals that live there germinate in 
the autumn, form a small rosette for the winter, and flower 
early the next year. When the hottest part of the summer 
is reached, and the sand is scorched by the sun, the plants 
die, leaving only their seeds to meet the hardships of 
