68 THE AMERICAN BOTANIST. 



gradual freezing the water in the protoplasm is drawn out 

 through the cell wall and forms minute ice crystals between 

 the cells in the intercellular spaces. When thawing begins, 

 the water is again absorbed by the protoplasm and the plant 

 is unharmed. Freezing is thus seen to have the same effect 

 upon the protoplasm as drying. If the frozen plant is suddenly 

 thawed the protoplasm is often unable to take up the water 

 rapidly enough for its purposes and so dies. Similarly the 

 sudden freezing of the plant may cause the ice crystals to form 

 within the cell and possibly kill it by rupturing the cell-wall 

 and its protoplasmic lining. With this explanation it is easy 

 to see the sense in the gradual thawing out recommended 

 for house plants that have been frozen, and also for the practice 

 of plunging such plants into cold water or sprinkling them 

 with it. 



RoSELLE. — In the hunt for food, man has been guided only 

 by his palate and has secured additions to his diet from any 

 part of the plant kingdom or any part of the plant that may 

 be of use. Fruits and seeds may be considered the only parts 

 of the plant that were manifestly designed to be used as food, 

 but man eats the food stored in the roots of the carrot and the 

 like, that stored in the stem of the potato and artichoke, that 

 in the leaves of onion and cabbage, that in the leaf-stalk or 

 petiole of rhubarb and celery, that in the flowers of cauliflower 

 and various tropical plants and even the pollen of some plants 

 is made into bread. There are few plants, however, in which 

 the calyx alone forms the edible portion, but this is true of the 

 Jamaican sorrel or roselle (Hibiscus sabdariffa) which our 

 government is trying to introduce into cultivation in the warm- 

 er parts of our country. As may be seen by the generic name 

 the new plant is related to the hollyhock, cotton, okra and 

 marsh mallow, but it is unlike in having an enlarged and in- 

 tensely sour calyx. This is recommended as excellent for jelly- 



