﻿2 28 BOTANICAL GAZETTE [march 



A STUDY OF THE VEGETATION which has appeared upon Krakatoa since 

 the destructive eruption of 1883 was made by Penzig ^'^ in 1897. The plants 

 and their distribution he found in harmony with what could be expected from 

 the report of the study made by Treub in 1886. The beach flora is the 

 characteristic Pes-Caprae-formation of tropical islands, about twelve species 

 composing it here. Beyond the beach, covering the lava hillocks and valleys, 

 very tall grasses ( Gymnothrix elegaits^ Saccharntft spontanetmi, and Phragmites 

 Roxbiirghii) intermixed with vines {Scaevola Koenigii, Ipo?ncea^ Vigna, etc.) 

 predominate. Shrubs and other species are but isolated, so the vegetation 

 may well be distinguished as a savanna. Above this, on the cliffs, ferns 

 grow abundantly ; while upon the more exposed rocks Cyanophyceae do the 

 work performed in higher latitudes by lichens. In all 62 species (50 seed- 

 plants and 12 vascular cryptogams) were found, as compared with 15 seed- 

 plants and II ferns over ten years earlier. No mangrove trees grow about 

 Krakatoa, nor as yet forest trees upon It. As to the means by which the island 

 was seeded, it was learned that 60.39 per cent of the plants owe their arrival 

 to ocean currents, 32.07 per cent, to the wind, and 7.57 per cent, to animals. — - 



Etoile B. Simons. 



The life history of Ruppia rostellata is described in a recent paper by 

 Murbeck.^7 It is suggested that pollination may take place under water as 

 well as at the surface, although definite proof was not obtained. During the 

 development of the microspores the tapetal cells break down, and their 

 nuclei float free in the liquid which fills the cavity of the microsporangium. 

 The formation of two definite male cells within the irres^ularly elongated 



pollen grain was traced in detail. A tapetal cell is formed, and the megas- 

 pore mother cell gives rise to four megaspores which are not arranged in a 

 row, but the two lower spores lie one above the other while the two upper 

 ones lie side by side or somewhat obliquely. This arrangement was observed 

 in numerous instances. In one peculiar case the archesporial cell seems to 

 have divided obliquely instead of by a pericline, and both resulting cells 

 show the distinguishing characters of megaspore mother cells. In this mitosis, 

 by which the archesporial cell gives rise to the tapetal cell and megaspore 

 mother cell, the number of chromosomes was found to be sixteen. This 

 number was also counted in other sporophytic cells. In the first division of 

 the megaspore mother cell and also in the microspore mother cell the number 

 is eight. The polar nuclei fuse completely before fertilization. Although 

 the pollen tubes were traced to the embryo-sac, the actual process of fertil- 

 ization was not observed. At the first division of the endosperm nucleus a 

 wall is formed, dividing the sac into two chambers. The chamber at the 



^* Penzig, O., Die Fortschritte der Flora des Krakatau. Ann. Jard. Bot. Buitenzorg 

 x8 : 92-113. 1902. 



'7MURBECK, Sv,, Ueber die Embryologie von Ruppia rostellata Koch. Kongl. 

 Svensk. Vetensk. Akad. Handl. 36: 1-21. ph, 1-3, 1902. 



