86 TUFTS COLLEGE STUDIES, VOL. II, No. 3 



masses, but very few have to be sought below low water mark. 

 In the extreme north the temperature and the shore ice permit 

 practically nothing to exist uncovered by water, and all algae 

 must be obtained by dredging. The same result is reached, in 

 part, in the subtropical waters of the West India region, but by 

 different causes ; tides are slight and irregular, and exposure for 

 any length of time to the intense sunshine would be fatal to 

 delicate forms ; here also one must look below the surface. 



In many genera of marine Chlorophyceae the individual 

 plants are large enough to be easily seen (Ulva, Cladophora, 

 Udotea, etc.) but for the greater part only the mass, not the 

 individual, can be distinguished (Rhizodonium, Codiolum, etc.) 

 while others appear as a thin film on wood or stone (Pseudendo- 

 clonium, Pilinia, etc.) or as a coloration of the shell in which they 

 are imbedded (Gomontia). Then there are endophytic forms 

 (Bolbocolcon, Chlorochytriu-ni) not at all manifest, and only to be 

 found by dissection of the host plant. These conditions being 

 so varied, the only safe course for a student is to collect every- 

 thing of a green color that he does not recognize. Few of the 

 marine green algae are specially sensitive ; in most cases they 

 can be kept a reasonable time immersed in salt water, or packed 

 in cloths moistened with salt water, if not subjected to higher 

 temperature than that of the water in which they grew ; but if 

 plants or portions of plants to be studied must be kept for sev- 

 eral days, it is better to keep them in salt water to which 

 enough ordinary formalin (formaldehyde) has been added to 

 make a three per cent, solution. Of course no action of the 

 living plant can then be observed, but the structure is main- 

 tained practically intact for months, as far as would be needed 

 for anything described in this work. For permanent preserva- 

 tion of these algae, nothing is better than the herbarium form. 

 In many genera whatever characters are needed for systematic 

 purposes can be obtained from herbarium specimens, and in 

 those cases where characters cannot be made out as satisfac- 

 torily in the dried specimens as in fluid preparations, at any rate 

 whatever is available continues so for an indefinite time, while 

 it is only too common to find a fluid preparation worthless. As 

 regards microscopic slides, they can be prepared so as to show 



