PLVUS SYLVESTRIS. 169 



the fern the asexual plant produces spores, and that in 

 Selaginella, a more advanced type, it does also, but of 

 two sorts. Does the pine likewise produce spores ? 

 Certainly, although we have so long called them pollen, 

 that we are inclined to forget their true relation, 

 which would be better indicated by the term pollen 

 spores, used by DeBary. 35 These pollen spores cor- 

 respond to the microspores of Selaginella, and like 

 them have the prothallium reduced to one or a few 

 cells, but unlike them do not produce antherozoids. 

 This, however, is a matter of adaptation. Wherever 

 there is water to transport the fertilizing element 

 from the male to the female organs, it is usually 

 an active body (antherozoid), as in Adiantum, Atri- 

 chum and Marchantia, with an exception in Spirogyra, 

 while if it must be transported through the air or the inte- 

 rior of plant tissues a tube leads from the antheridium 

 to the archegonium as in Microsphaera and Cystopus. 

 Pine like other flowering plants has the spores carried 

 bodily through the air in order to bring them into 

 proximity to the female element, then a tube (pollen 

 tube) develops, which connects the male and female 

 organs. Turning now to the female part, which cor- 

 responds to the macrospore of Selaginella, it (now called 

 the embryo-sac) is found so greatly reduced that it 

 never leaves the place in the mother plant where 

 formed. The prothallium is represented by the pri- 

 mary endosperm. The archegonia themselves are 

 much simplified as might be expected. They arise 

 from superficial cells of the endosperm (prothallium). 



35 Morph. u. Biolog. d. Pilze, Mycet. u. Bacterien, 1884, p. 140. 



