1908] KILDAHL—PHYLLOCLADUS ALPINUS 345 



and states that there are eight to sixteen free nuclei. Jager (13) 

 found sixteen free nuclei in the proembryo of Taxus baccata; and 

 Coulter and Land (9) found four free nuclei in Torreya taxijolia. 

 One of the older ovules showed a long suspensor and an embryo of a 

 few cells buried near the base of the gametophyte (fig. 33), but it was 

 impossible to make out its structure. 



Summary 



The microsporophyll has two abaxial sporangia and the micro- 

 spores are shed on November 1 or before. 



Two prothallial cells are formed, the first of which is generally 

 evanescent; sometimes both persist as free nuclei, the walls of both 

 being evanescent. 



The mature microspore has usually four free nuclei, and occa- 

 sionally five. 



The ovulate strobilus is borne on the phylloclad, and bears two to 

 eight ovules. 



The ovule has two integuments; one thick and fleshy, the other 

 (arillus) thin and leathery and persistent only at the base. They 

 are free from the nucellus to its base, and contain no vascular strands. 



Microspores are found resting on the top of the nucellus on Novem- 

 ber 1, and occasionally pollen tubes and archegonia are formed at 

 this date. 



Pollen tubes are very numerous and pass in a comparatively 

 straight line through the nucellus to the archegonium. They smash 

 the neck cells, if there are any, and empty their entire contents into the 

 egg; the contents of one or more pollen tubes were found in an egg 

 after the eight-nucleate stage of the proembryo. 



The body cell divides into two equal male cells just before dis- 

 charge into the egg; and only one male cell functions. 



The archegonium is surrounded by a heavy jacket layer, consisting 

 of multinucleate cells with large nuclei. Two neck cells are probably 

 formed. No ventral cell or nucleus was found, but the material does 

 not justify a definite statement as to its occurrence or not. 



The male cell is surrounded by a cytoplasmic sheath which, partly 

 at least, surrounds the fusion nucleus. 



At least eight free nuclei are formed by the proembryo before cell 

 walls are formed ; and a long suspensor is developed. 



