No. 454.] STUDIES ON THE PLANT CELL. 745 



firming the conclusions of Mottier that these structures are 

 developed here after the same rnethods as in the pollen mother - 

 cell, from surrounding investments of fibrillse and without cen- 

 trosomes. Indeed the embryo-sac is remarkable for the quan- 

 tity of the cytoplasmic fibrillae present during its mitoses. 



In concluding this account attention should be called to 

 some forms whose microspore mother-cells were formerly sup- 

 posed to omit the mitoses of sporogenesis and develop directly 

 into pollen grains. These conditions were reported in Zbstera, 

 the Cyperaceae, and the Asclepiadacese. However, Juel (: 00) 

 finds the two mitoses present in Carex acuta, although three of 

 the nuclei break down and the cytoplasm is appropriated for the 

 fourth to form a single pollen grain whose wall is developed 

 from that- of the mother cell. The history is very similar to 

 the development of the megaspore in certain heterosporous pteri- 

 dophytes {e.g., Marsilia, Selaginella) and to the embryo-sac, 

 which functions while its companion polential megaspores degen- 

 , erate. The development of the pollen in the Asclepiadacese has 

 been shown to be normal in the nuclear activities by several 

 investigators (Frye, :oi, Strasburger, :oi,and Gagner, :02), the 

 tetrad consisting of four pollen grains in a row, instead of the 

 usual arrangement. In Zostera (Rosenberg, :oi) there are lon- 

 gitudinal divisions of the very much elongated pollen mother-cell 

 to give four extraordinary filiform pollen grains. 



5. The Coenocyte. 



This remarkable type of cell has reached an extraordinarily 

 high state of development in certain plants, notably among the 

 Siphonales and the filamentous Phycomycetes (Mucorales, Sap- 

 rolegniales and Peronosporales). Coenocytes are multinucleate 

 cells. The simplest types are developed by the limited division 

 or fragmentation of a nucleus accompanied by an increase in the 

 size of the cell but without extended growth. Excellent illus- 

 trations are found in the older cells of the red algae, the inter- 

 nodal cells of the.Characese and in old parenchyma cells of many 

 higher plants. 



A higher type of coenocyte is presented when the multinuclcr 



