482 



BOTANY 



i. 442. Ceratozamia longijolia. Lonj:i- 

 tuilinal section through a youni: ovule, 

 showing the nucellus (l), including a 

 lar^e group of sporogenous cells (spor.) 

 and tin- integument (/) (After TREUB. 

 x 33.) 



Fi<;. 443.--2VWM.V Ixtccat'a. Longitudinal section 

 through tli' sport igenous tissue, showing an 

 embryo-sac mother-cell which has undergi'iie 

 the t trail division; three of tlie fai'iiltat i\ > 

 niacri)s])oi-es are degenerating, while the fourth 

 is undergoing further development, (x 2">0.) 



generative cells, while Taxus has 

 only one. In the Cycadinae and 

 Ginkgoinae the male cells appear as 

 spermatozoids, while in the other 

 Gymnospenns they are smooth cells 

 not provided with a cell wall. 



In many Gymnosperms the 



FEMALE FL4IWKKS or <.'<>NK* 



resemble the male flowers in 

 being composed of an axis 

 bearing numerous, spirally ar- 

 ranged sporophylls. In other 

 cases they differ from this 

 type in various ways, which 

 will be described in the special 

 part below. 



As a rule the macrosporophylls 

 bear two macrosporangia ; these 

 consist of a nucellus and usually 

 a single integument. The nucellus 

 often becomes of large size by the 

 numerous periclinaldiviriona which 

 take place in the more superficial 

 layers of cells. In the same way the 

 sporogenous tissue, which origin- 



ic. 444. Median longitudinal section of an ovule ates immediately below the i-pider- 

 of I-icca culyans. e, Emliryo-.siic tilleil with the pro- n ,j Sj becomes deeply placed by the 

 thallium ; n, archegonimn showing ventral (o) and rati<m of Iiumero u8 layers of 



neck portion (c) ; >t, nucleus of e^'g-cell ; nr, nucellus ; ' 



p, i^iien-raius ; /, ix,iien-tui. : t, lategomnti , cells - Notwithstanding the con- 

 -Ainj.'. siderable size of the sporogenous 



