122 



ELEMENTARY STUDIES IN BOTANY 



ures among Seed-plants as stamens, pollen sacs, and pollen 

 grains, correspond to the microsporophylls, microsporangia, 

 and microspores of the Pteridophytes. 



Since stamen is so much more convenient a term than 



microsporophyll, the cone 

 which bears microspo- 

 rangia (pollen sacs) may 

 be called the staminate 

 strobilus or staminate cone, 

 but it should be realized 

 that " stamen " is only 

 another name for the 

 microsporophyll of Seed- 

 plants. It is the stami- 

 nate cone that is often 

 called a " male cone," 

 which is no more appro- 

 priate than to call the 

 ovulate cone a " female 

 cone." Also, there is no 

 objection to calling the 

 microspores " pollen," 

 provided it is remembered 

 that " pollen " is only 

 another name for the mi- 

 crospores of Seed-plants. 

 71. The ovule. It is 

 the ovule (megasporan- 

 gium) that distinguishes 

 Seed-plants, for it devel- 

 ops into the seed, and 



therefore it must differ somewhat from the megasporangia 

 of Pteridophytes. If it is cut through lengthwise, its general 

 structure will be evident (Fig. 98, A). On the outside of it 

 there is a covering which is loose above and extends into a 



A B 



PIG. 98. A, section of scale of ovulate cone, 

 showing the bract beneath (6), the scale 

 (s), the ovule (o), with its integument and 

 nucellus, and within the nucellus the mega- 

 spore (0) which probably contains the be- 

 ginning of the female gametophyte ; B, a 

 section through the ovule a year later, 

 showing the large female gametophyte (g) 

 with two archegonia (a) which are being 

 reached by pollen tubes (t) penetrating the 

 tip of the nucellus; observe also the in- 

 tegument at the top of the ovule with its 

 passage way (micropyle) to the nucellus. 



