The " Bed Snow " Plant. By G. S. West. 29 



being so easily destroyed by sudden changes in light and tempera- 

 ture. Both Kny and Kerner have shown that red colouring matters 

 are probably concerned in the conversion of light-rays into heat, 

 and the great value of such a function to the " red snow " plant is 

 at once obvious. Moreover, Hazen has pointed out that in the 

 closely related Sphcerella lacustris, more red pigment is habitually 

 developed in cultures made from material collected from places 

 frozen for a great part of the year, than in those made from 

 material collected in milder climates. 



The life-history of this organism is briefly as follows. The 

 typical resting-cell forms four daughter-cells of a similar bright 

 red colour, which remain for a time within the wall of the 

 mother-cell. So long as unfavourable conditions supervene, these 

 daughter-cells remain in the resting state, although often with a 

 slight increase in size. Should the conditions become favourable, 

 however, the daughter-cells very quickly escape from the mother- 

 cell, develop a pair of cilia, and become motile. Each is now a 

 zoogonidium (or asexual motile gonidium), and in this state the 

 cell generally increases in size. The cell-wall is thin and dis- 

 tended, standing out from the main body of the protoplast ; but 

 much detailed observation is yet required on the motile state of 

 Sphcerella nivalis. After a longer or shorter active period, the 

 zoogonidium returns to the resting state, and the main body of the 

 protoplast develops around itself a thick wall within the delicate 

 wall it possessed in the motile state. A sexual method of repro- 

 duction by the conjugation of isogamous planogametes (" micro - 

 zoogonidia ") has been described. The resulting zygospores are 

 said by "Wittrock to be verrucose at maturity. 



Sphcerella nivalis appears to have adapted itself to very low 

 temperatures, but it does not stand alone in this respect. There 

 are several algfe, belonging to widely separated groups, which live 

 habitually in the snow, and form a small assemblage of plants 

 known as the Cryoplankton. 



Prolonged exposure to a low temperature is physiologically 

 necessary for the " red snow " plant, otherwise it loses its vitality. 

 Chodat has stated that this alga will not live for any lengthened 

 period at a temperature above 4° C, but experiments conducted 

 both in this country and the United States do not entirely support 

 this statement, as the resting-cells can be kept alive in water for 

 over twelve months at ordinary outside temperatures. 



The distinctions between Sphcerella 'nivalis and S. lacustris are 

 not very great, and many authors have considered them to be 

 specifically identical. The only difference of importance appears 

 to be the presence in the motile vegetative cells of S. lacustris of 

 protoplasmic threads connecting the central mass of theprotoplnsi 

 with the outstanding cell-wall, whereas in S. nivalis these threads 

 are absent. Wollenweber states that S. lacustris has numen 



