138 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



plasm soon appear to be stretched. The chromatin and nuclear 

 substances now dissolve and impart their staining properties to 

 the entire cell contents. This is followed by a complete disor- 

 ganization of the cell contents. The pollen grains may have 

 formed mature walls before their cytoplasmic content disinte- 

 grates so that a considerable number of empty pollen grains have 

 been found in Drosera longijolia, D. binata, D. rotundifolia, D. 

 intermedia, and D. filijormis. There is considerable danger of con- 

 fusing these disintegration stages with badly fixed or over-stained 

 cells. 



The pollen grain. — The pollen grains of the Droseraceae are 

 unlike those of most species of plants in that the four pollen 

 tetrads remain permanently united. While the fact is of common 

 knowledge no adequate figures of these tetrad grains have been 

 published. Drude ('91) figures the pollen grains oi Drosera rotundi- 

 folia. He shows four pollen grains arranged in a tetrahedron and 

 the outer surface of each grain thickly covered with spines. Drude 

 also shows a number of tubules which arise from the angle formed 

 by two adjacent pollen grains in the tetrad. He holds that these 

 tubules are pollen tubes and are formed after the pollen reaches 

 the stigma. Only one or two of them are functional and grow 

 out to penetrate the style. Drude does not show the structure 

 of the pollen grain in section nor does he describe the origin or the 

 exact position of the tubules. Diels ('06) accepted these observa- 

 tions although he apparently never studied these tetrads himself. 

 Rosenberg ('99) has also studied the pollen grains of Drosera 

 rotundifolia. He also refers to these tubules as pollen tubes but 

 correctly observes that they are formed before the pollen is dis- 

 charged from the anther. He characterizes them later ('09) as 

 pollen tube anlage which appear in great numbers as a crown sur- 

 rounding the (base) external contact edges of the pollen grain. 

 Rosenberg gives a number of text figures of sections of pollen 

 grains; they are all inadequate and in some respects inaccurate. 

 He gives no description of the origin of the tubule, though it 

 appears from some of his figures that these tubules arise from the 

 apex of the tetrahedral pollen grain. 



The material of Drosera Ion gif alia sent to me by Professor 

 John Davidson and of Drosera binata which I obtained at The New 

 York Botanical Garden was very favorable for the study of the 



