622 BOWMAN— ECOLOGY AND 



the endosperm completely surrounds the unanchored embryo and 

 permits of motion in different places by the growth of the embryo. 

 Of both these cases Karsten says (p. 33, 1. c.) : " Die Rolle eines 

 Reservestoffe speichernden Gewebes kommt aber dem Endosperm 

 weder im ersten, noch im zweiten Falle zu." 



It remained for Haberlandt, however, to do the most intensive 

 work on these endosperm cells. The plants which he investigated 

 at Buitenzorg were Bruguicra, JEgiceras and R. mucronata. For 

 the first two genera he has learned that the endosperm forms many- 

 celled haustoria, which grow into the tissue of the integument and 

 absorb the food for the embryo (p. 95, 1. c). However when he 

 came to R. mucronata he expected to see the same development 

 even to a greater degree, on account of the rapid growth of the very 

 long hypocotyl, but a quite different condition was found, different 

 even from that found by Warming for our species, R. mangle. 



The inner rounded end of the embryo is connected with the integ- 

 ument by a well-developed " Saugorgan " structure consisting of 

 cells of several layers, with thin walls and rather elongated in out- 

 line, the upper layer of which is supplied with warts and papillae, 

 which apparently transfer food to the embryo. But the endosperm 

 cells around the cotyledonary collar region have large thin-walled 

 watery cells, among which the absorptive papillae are more numer- 

 ous. Haberlandt shows this in a series of excellent figures (1. c, PI. 

 XL), but that these papillae merely function as, or are absorptive 

 organs, Haberlandt does not concede. His conclusion is that this 

 tissue is an enzyme-secreting layer of cells which perhaps secretes 

 diastase, and to prove this he placed starch grains on these papillae 

 and learned that in twenty-four hours the grains on the rounded 

 head region were deeply corroded, while those of the collar were 

 less so. The large w'atery cells of the latter region Haberlandt re- 

 gards as water reservoirs for the delicate absorptive tissue of the 

 " head " region. This he regards as a special adaptation to the 

 physiologically dry habitat of the mangrove and a protection against 

 transpiration."^ 



In the more recent work of Cook there is also mentioned (1. c, 

 p. 273) the fact that the cells of the integument are much denser 



01 Haberlandt, G., loc. cit., p. 105. 



