Fig. 356. — Ephedra mridis: longitudinal section of ovulate flower, showing some of the details diagrammed in fig. 355. — From an unpublished drawing by Dr. S. Flowers 



There are more bracts than in the staminate strobilus, usually 

 four or more pairs of sterile ones, and a terminal ovule. The ovule 

 has two integuments, the outer consisting of four bracts, coalescent 

 at the base, and the inner, of two bracts, also coalescent at the base, 

 and, at maturity, splitting at the top. The inner integument, at the 

 time of pollination, elongates immensely, and, at its tip, is a spark- 

 ling polUnation drop. The topography of the ovule at this stage is 

 well shown in the much copied figure by Land-*^* (fig. 355), and in a 

 recent figure by Flower (fig. 356). 



Strasburger found a row of three megaspores in Ephedra campy- 

 lopoda, and Jaccard found the same number in E. helvetica. Land,"* 

 in E. trifurca, found about equal numbers of threes and fours (fig. 

 357). Of course, in rows of three, only the lower two are megaspores: 

 the upper one is still a 2X cell of the sporophyte. 



THE GAMETOPHYTES 



Gametophytes of Eastern Hemisphere species have been studied 

 by Strasburger,s«^ Jaccard,'*' Pearson,''''" Berridge and San- 

 D.w,''* and Dr. Stephanie Herzfeld.'" Land's"*' "' work on the 

 American Ephedra trifurca is the most complete account. 



374 



The male gametophyte. — Ephedra trifurca will serve as a type. As 

 in all seed plants, the microspore is the first cell of the male gameto- 

 phyte. At its first division, a prothallial cell is cut off by a wall. 

 At the second division a prothallial nucleus is formed, but there is no 

 wall separating it from the rest of the spore, which is the antheridium 

 initial (fig. 357). The initial then divides, forming a tube cell and a 

 generative cell, which divides to form the nuclei of stalk and body 

 cells. These two nuclei he in a common mass of cytoplasm, and are 

 never separated by a cell wall. At this stage the pollen is shed. 



When it reaches the ovule, the generative cell divides, giving rise 

 to two nuclei which are alike in size and appearance. The e.xine 

 cracks longitudinally, and the intine slips out, becoming prolonged 

 into a short pollen tube (fig. 358). 



The female gametophyte. — The megaspore is the nrst cell of the 

 female gametophyte (fig. 359). Its germination begins, as in all gym- 

 nosperms, with a period of simultaneous free nuclear divisions 

 (fig. 359 B). The free nuclear period lasts about 20 days and walls 

 begin to appear at the 256 nucleate stage (about April i, in 1903, 

 which was a very dry season). 



Wall formation begins at the outside and rapidly proceeds to<.ard 



