January 29, 1904.] 



SCIENCE. 



177 



course is down the floral tube, thence di- 

 rectly through the ovarian cavity to the 

 upturned mieropyles of the ovules. The 

 pollen tubes that have failed to enter 

 ovules often swell up at their tips into 

 tuber-like enlargements, which may be 

 fifteen times the normal diameter of the 

 tube. In these tubers which lie amcng the 

 ovules, the male elements can be made out, 

 each distinctly a cell, rather than a nucleus 

 only. About each male nucleus, which 

 usually shows a nucleolus, is an ample cy- 

 toplasm bounded by a membrane. The 

 functioning pollen tubes pass through the 

 micropyle and seem to enter one of the 

 synergids. Numerous preparations showed 

 one sperm in contact with the egg nucleus, 

 and in several instances the second sperm 

 was found fusing with the endosperm nu- 

 cleus. The egg regularly divides before 

 the primary endosperm nucleus. The 

 functioning pollen tubes persist for a long 

 time, sometimes until the embryo is well 

 developed. 



Protliallia of Botrycliium ohliquum: H. ,L. 



Lyon. 



During the summer of 1903 gameto- 

 phytes of Botrychmm ohliquum were col- 

 lected in considerable numbers in Minne- 

 sota. In shape they resemble those of B. 

 Virginianum but average only about one 

 third the size of the latter. The repro- 

 ductive organs are borne dorsally and do 

 not differ essentially from those of other 

 Ophiogiossaceas described. The embryo 

 sporophyte is bipolar instead of tripolar 

 as in B. Virginianum, the stem growing 

 directly upward and the root directly 

 downward through the pr.othallitun. There 

 is no pronounced nursing-organ. All the 

 superficial cells of that portion of the em- 

 bryo lying within the tissue of the gameto- 

 phyte apparently act as absorbent cells. 

 The primary root usually protrudes 1 to 3 



cm. from the prothallium before the first 

 leaf bursts through the calyptra. 



The Life History of Ephedra trifurca: W. 



J. G. Land. 



Material for a morphological study of 

 Ephedra trifurca was obtained in the vi- 

 cinity of Mesilla, N. M. Collections were 

 made at regular intervals between Decem- 

 ber 20, 1902, and May 20, 1903. The pri- 

 mordium which gives rise to the staminate 

 flowers was apparent in the first material 

 collected. The perianth appeared a month 

 later. The primary wall cell divides to 

 form two layers, the wall cell and the tape- 

 tum. The microspore mother cells remain 

 in the resting condition about one month. 

 The reduction division occurs about March 

 15. The gametophyte number of chromo- 

 somes is twelve. The male gametophyte 

 at the time of the shedding of the pollen 

 grain consists of two prothallial cells, tube 

 nucleus, stalk cell and body cell. The body 

 cell divides shortly before fertilization 

 occurs. The ovule has two integuments: 

 an outer one resulting from the fusion of 

 four bracts, the inner one from the fusion 

 of two bracts. The megaspore mother cell 

 appears about March 8. Sometimes two or 

 three megaspore mother cells are present, 

 but only one megaspore functions. As the 

 result of the division of the megaspore 

 mother cell a row of four or sometimes 

 three megaspores is formed, the lowest 

 one being of course functional. The di- 

 vision of the megaspore is followed by free 

 nuclear division and parietal placing. At 

 least 256 nuclei are formed before walls 

 appear. One, two or three archegonia are 

 formed, and the central cell is placed 

 deeply in the tissues of the gametophyte. 

 The ventral nucleus is cut off shortly be- 

 fore fertilization, which occurred the pres- 

 ent year about April 20. The oospore 

 forms from two to eight free nuclei, each 

 one of which oro'anizes a wall and gives 



