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 (Pedicular is 

 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 (CaTcile 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 



