272 SUMMARY OF CURRENT RESEARCHES RELATING TO 



flowers are dioecious and trirnerous, the outer stamens being represented 

 by staminodes. In the prophase of the heterotypic division the chro- 

 matic threads of the pollen-mother-cell are parallel to one another ; 

 subsequently they break up to form sixteen double chromosomes. Two 

 forms of tetrads have been observed ; usually the four cells lie all in 

 one plane ; less often there is a double tier of cells with two cells in each 

 tier. The division of the primary pollen-nucleus and the formation of 

 the generative cell occur simultaneously in all the cells of the tetrad. 

 The generative cell is spindle-shaped and it lies freely in the pollen- 

 grain, where also its division takes place. The archesporial cell arises 

 in the sub-epidermal layer of the nucellus, without any division into 

 tapetal cells and embryo-sac-mother-cell. The antipodal cells degenerate 

 very early, and at the same time fusion takes place between the two 

 polar nuclei and the primary endosperm-nucleus. The egg-cell is 

 smaller than the synergidas. The greater part of the outer wall of the 

 nucellus and also of the inner integument soon begins to cuticularize. 

 Several pollen-tubes may enter one micropyle, and two have been seen 

 to enter one embryo-sac ; double fertilization takes place. The first 

 division of the fertilized egg-cell occurs after the formation of several 

 free endosperm-nuclei; The embryo remains undeveloped and without 

 a distinct suspensor. The primary endosperm-nucleus divides in the 

 middle of the embryo-sac ; one daughter-nucleus gives rise to the 

 endosperm, while the other passes to the antipodal end and forms the 

 nucleus of a haustorium, which gradually empties before the ripening 

 of the seed. Endosperm is the result of free nuclear division, and each 

 cell is multinucleate, the number of nuclei varying with the size of the 

 cell ; the reserve-materials are starch and albumin. The seed-coat, is 

 formed from the cuticularized wall of the nucellus, the entire inner 

 integument, and the inner layer of the outer integument. 



Morphology and Anatomy of Hydrostachys.* — II. Schloss has 

 studied the vegetative organs of H. nataUnsis, a plant occurring locally 

 and completely submerged in the mountain-waterfalls. The short fleshy 

 rhizome bears adventitious roots ou its sides and lower surface, while 

 leaves arise among the lateral roots and from the upper surface. Each 

 leaf has two stipules fused with one another and with the base of the 

 petiole to form a sheath, which encloses a younger leaf. The leaves 

 vary much in size and form ; the primary leaves are fi to 8 mm. long, 

 and are more or less simple, while the stipules are represented by minute 

 notches ; the leaves of the full-grown plant attain a length of 35 cm. 

 and a breadth of 8 cm., and are usually bipinnate. Similar variations 

 occur in the petiole. The fern-like appearance of the leaf is due to a 

 number of outgrowths occurring on the petiole and blade of even the 

 youngest leaves. The author regards these outgrowths as emergences, a 

 theory supporting the relationship of the Hydrostachyaceas and the 

 Podostemacea?. The anatomy of the leaves resembles that found in 

 H. imbricata, but in addition to the vascular bundles, isolated strands 

 pass from the base of the petiole to the emergences. The latter consist 



* SB. Akad. Wiss., cxxii. (1913) pp. 339-60 (4 pis. and 10 figs.). 



