THE VERBENA FAMILY 361 



gave birth to barnacle-geese, which dropped from the seeds, 

 placidly into the water below them a truly appalling meta- 

 morphosis ! 



With all their ingenious contrivances, the young Rhizophoras y 

 however, may sometimes be found cast up in the drift left by 

 the falling tide on the shore. In Avicennia the embryo is 

 provided with two large fleshy cotyledons, which present the 

 extraordinary and almost unique feature of being unaccom- 

 panied by any trace of a rootlet. 



Although well developed, it does not fall from the husk 

 before it leaves the tree. The whole seed drops to the mud. 

 There it splits and allows the embryo to escape. The plantlet, 

 as in Cuscuta (v. p. 345), shows wonderful vitality. As the 

 cotyledons possess a large food supply, the embryo may 

 remain drifting with the tide for weeks without a holdfast, 

 and yet survive. Generally, however, it quickly attaches 

 itself to the mud by putting forth four or five adventitious 

 rootlets, which are so arranged as to give the maximum 

 support possible. They are stout, stiff, and divergent, and 

 penetrate the mud at an angle of 50 or 60 with the 

 surface. 



The descriptions given of the germination of the mangrove 

 in Dendy and Lucas's Botany, Kirk's Forest Flora, and other 

 standard works, are quite erroneous. Kirk's description, also, 

 contains various other errors, in addition to those already 

 pointed out. He states that the tree only attains its greatest 

 luxuriance in deep water. On the contrary, the tree never 

 grows in deep water, and its luxuriance depends largely on 

 the depth of the mud in its vicinity. The wood is described 

 as being white, straight in the grain and perishable, whereas 

 it is brown and durable, with the fibres arranged in layers 

 which cross each other diagonally, thus making it difficult 

 or impossible to split, except on the round. 



Much work has yet to be done on the development and 

 germination of the embryo in Avicennia. 



