PLANTS OF SPECIAL INTEREST. 65 



textile species occurs on the island no fruit of course is produced by 

 it. The importance of collecting the flowers and preserving them 

 carefully in alcohol or formalin is evident, as well as the necessity of 

 making photographs of the growing tree to show its habit, the char- 

 acter of its bark, its method of branching, its fascicles of leaves, and 

 the emergences on its stem and aerial roots. 



BANYANS, MANGROVES, AND EPIPHYTES OF THE FOREST. 



Of special interest on account of their method of germination and 

 growth are the giant banyans {Ficus spp.) of the forest, the mangroves 

 of the brackish estuaries, and certain epiphytal cryptogams and other 

 plants. 



The banyans usually begin their existence upon other trees, sending 

 down aerial roots which interlace and grow together, clasping the 

 trunk of their host and eventually strangling it. They then lead an 

 independent existence, their great spreading limbs sending down more 

 roots, which are like pendent threads at first, but soon thicken after 

 gaining a foothold in the earth, and serve as columns to support the 

 great dome of foliage overhead, as well as to supply it with nourish- 

 ment and moisture (PI. VIII). 



The chief interest in the mangroves (Rhizophora and Bruguiera) lies 

 in the fact that their fruit germinates while still attached to the tree, 

 the spindle-shaped radicle perforating the apex of the fruit, elongating 

 and hanging vertically downward. When the fruit falls the radicle 

 sticks into the soft mud below, retaining an upright position, like a 

 stake thrust into the ground, and resisting the current of the tide as 

 it ebbs and flows. 



The forest epiphytes are not well known, owing to the difficulty in 

 collecting them. Care should be taken to visit clearings where forest 

 land is being prepared for planting. In such places good material can 

 undoubtedly be collected. The most interesting epiphyte thus far col- 

 lected in Guam is Dischidia pvherula, which belongs to a genus hav- 

 ing some of their fleshy leaves modified into urn-like receptacles. 

 These usually contain water, and the adventitious roots of the stem 

 often creep into them, as if for nourishment or moisture. 



PLANTS THAT SLEEP. 



Among the Guam plants there are a number which exhibit in a 

 marked degree the phenomenon known as " sleep movements," folding 

 their leaves each night and opening them again at sunrise. Some of 

 them {Acacia famesiana and Ahrus ahnis, PI. XXXII), are so sensi- 

 tive to changes in the intensity of light that they go to sleep if the 

 sky suddenly becomes overcast, and wake up when the sun reappears. 

 Most of these plants are leguminous, but there is one remarkable 

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