428 BOTANICAL GAZETTE v z 



Methods 



Plants of this alga, either whole or cut into lengths of 5-10 mm. 

 each, were fixed in medium chromo-acetic solution, or in Flemminz 5 

 fluid, within a few minutes after being collected. As the alga is 

 very gelatinous, great care was taken that all changes in the alcohols 

 should be made very gradually. The material on which the alcohol 

 was changed in 5 per cent grades showed considerably less shrinkage 

 than that on which the changes were made in 10 per cent grades. 

 Most of the paraffin sections used were 10 01 12 fi thick. Sections 

 2 fi thick were also used for cytological details. For staining. 

 Heidenhain's iron alum hematoxylin (1 hour in alum solution, 

 2 hours in hematoxylin) gave the best results. Acid fuchsin and 

 methyl green stained the spores very well, but were not satisfactory 

 for the vegetative structure. The triple stain, safranin. gentian- 

 violet, and orange G, was also used. The slipping from the slide 

 of sections of material fixed in Flemming's fluid occurred somewhat 

 frequently in consequence of bleaching the sections in hydrogen 

 peroxide. This difficulty was finally largely overcome by dipping 

 the slides into 0.5 per cent solution of celloidin in a mixture of 

 equal parts of alcohol and ether. 



Description 



HABITAT AND APPEARANCE 



Dumontia, at South Harpswell, grows in abundance in tufts in 

 the small tide pools and also on the rocks that are exposed to the 

 air at low water. On large round rocks which were much exposed 

 to the surf, female and tetrasporic plants of Dumontia were found 

 growing down almost to the lower limit reached by Clwndrus 

 crispus, that is, just below the mean low water level. There is 

 considerable variation in the size of the plants. The larger plants 

 were found in the more exposed places. The plants in the tide 

 pools near the low water mark were larger than the plants in the 

 higher pools, and the largest plants of all were those growing at low 

 levels on the round rocks. The color of the plants varies from a 

 rich dark red to a pale reddish yellow. [Mature tetrasporic and 

 female plants ranged in height from 4 cm. to 23 cm. There is 



