PHYSIOLOGY OF THE RED MANGROVE. 671 



(1230) to Catesby (1731) and the references in the taxonomic and 

 systematic writers from Linnaeus (1736) to the present. The allu- 

 sions to mangroves in the writings of the first two periods are 

 mainly quaint and interesting descriptions by travellers, explorers 

 and voyagers, while those of the last period are largely systematic. 



2. In the morphology of the root, a study of the cortex cells of 

 the submerged absorptive roots showed the thickenings or "ver- 

 dickungsleisten " of Warming to be really an artefact brought about 

 by a slight shrinkage of the walls of the delicate transfusion cells, 

 which are lightly connected with each other. 



3. The mechanical arrangement for the shedding of the pollen 

 from the multilocular anthers consists of two systems of cells in the 

 anther, the thin exothecial cells forming outer deciduous flaps, and 

 the heavily reinforced cells of the expanded connective area, which 

 have hitherto been overlooked. Dehiscence occurs by a rupture 

 along a definite line due to the strain on the exothecial cells produced 

 by their shrinkage and the resistance ofifered by the reinforced cells. 



4. A conception of the endosperm is here maintained in agree- 

 ment with that of Haberlandt, viz., that it functions as a placental 

 organ rather than as reserve material. 



5. By experiment the growth rate of emerging hypocotyls is 

 seen to be 4.7 centimeters in 34 days in Florida. 



6. In specially concentrated media a high mortality of seedlings 

 is shown to be due to the increased hydrogen ion concentration in 

 HjS mud cultures; and in cultures of i4oper cent, hyperconcentrated 

 sea water the mortality is due to the difficulty of absorption and 

 retarded metabolism. 



7. The transpiration rate records of this work show, first, for 

 the moist soil cultures, the rate of transpiration to be delicately 

 balanced with the amount of available moisture in the soil; second, 

 the concentration-culture rates show that plants in dilutions above 

 35 per cent, sea water, growing in New Jersey soil, transpire more 

 rapidly than plants in shell sand ; that for cultures in 35 per cent, 

 concentration of sea water and fresh water the transpiration is of 

 equal rate for either soil and finally that cultures in dilutions under 

 35 per cent, transpire more rapidly when growing in shell sand. 

 The same balance of relations is seen in the moist soil cultures at a 



