RHIZOPHORA MANGLE 



97 



the results would have been still more marked. It is well known 

 that these seedlings readily strike when stranded on a mud-flat, and 

 my observations show that they do the same on a sandy beach, 

 though often abortively. The point here investigated is their 

 capacity of postponing this process. 



On the Vitality of Seedlings of Bhizofhoba mangle which had been kept 

 Dey foe Five Months afteb being gathebed fbom the Tbee 



(They varied in length from 6-6 to 12-3 inches (168-312 mm.), and were detached 

 from the fruit-case. The experiment was carried out during June and July in 

 England in a greenhouse, and, therefore, under warm conditions. The measurements 

 were made from the base of the plumule to the tip of the hypocotyl.) 



Dried Seedlings 



Increase in Weight 



Increase in Length 



Five seedlings kept afloat between 

 4 and 5 weeks in fresh water. 

 Original length in dry state, 6-6 to 

 8-9 inches. 



17 to 25 per cent. 



0-2-0-3 inch(5-7£ mm.) 



Three seedlings kept afloat be- 

 tween 4 and 5 weeks in sea-water. 

 Original length in dry state, 6-6 to 

 12-3 inches. 



10 to 20 per cent. 



0-2 inch (5 mm.) 



Two seedlings kept afloat between 

 4 and 5 weeks in sea-water. Original 

 lengths in dry state, (A) 8-9 inches. 

 (B) 12 inches. 



(A) 54 per cent. 



(B) 48 per cent. 



(A) 0-6 inch (15 mm.) 

 (B) 1-0 inch (25-4 mm.) 



1 



All the seedlings were much shrunken, wrinkled, and blackish 

 along their whole length, with the exception of the lower end, which, 

 for a distance of from one to two inches from the tip of the hypocotyl, 

 retained a bright green hue and was less withered. Evidently the 

 seedlings in fresh-water regained only a part of the water that they 

 held in the living state, and the small increase in length of from 

 5 to 7 mm. was in the main the result of the swelling process. 

 Three of them placed in sea- water behaved like those in fresh- water, 

 and here it is also apparent that little or no actual growth occurred. 

 However, two of those in sea- water behaved very differently. They 

 absorbed, relatively speaking, twice or three times as much water, 

 and increased their length in the one case by 15 mm. and in 

 the other by 25 mm. The growth was hypocotylar, since the 

 measurements were made from the base of the plumule to the tip 

 of the hypocotyl. Rootlets were not developed. No effort was 

 made to unfold the plumular leaves, nor was there any marked 

 increase in length of the plumule, such as could be attributed to 

 growth. 



This experiment is interesting from the fact that it supplied its 

 own " control " in the case of the three seedlings that behaved in 

 sea-water like those in fresh-water and showed no active growth. 

 One of the implications is that Rhizophora seedlings, after falling 



H 



