SYNOPSIS 389 



PAGE 



39. Equisetum. 



Sporangia borne on sporophylls arranged in cones : 

 spores homomorphic : prothalli dimorphic (male and 

 female) ... 362 



40. Salvinia. 



Spores dimorphic : microspore produces vestigial male 

 prothallus : megaspore produces greatly reduced female 

 prothallus 364 



41. Selaginella. 



Microspore produces unicellular prothallus and multi- 

 cellular spermary, both endogenously : female prothallus 

 formed in megaspore and is almost endogenous : embryo 

 provided with suspensor . 367 



42. Gymnospenns. 



Cones dimorphic (male and female), with rudimentary 

 perianth : no sperms formed but microspore gives rise to 

 pollen tube, nuclei in \vhich are the active agents in fer- 

 tilization : single megaspore permanently inclosed in 

 each megasporangium : female prothallus purely endo- 

 genous : embryo (phyllula) remains inclosed in mega- 

 sporangium which becomes a seed . 369 



43. Angiosperms. 



Cone modified into flower by differentiation of sporo- 

 phylls and perianth : female sporophyll forms closed 

 cavity in which megasporangia are contained : mega- 

 spore produces a single ovary represented simply by an 

 ovum and two synergidae : formation of prothallus re- 

 tarded until after fertilization . . 374 



B. SUBJECTS OF GENERAL IMPORTANCE DISCUSSED 



IN SPECIAL LESSONS. 



I. CELLS AND NUCLEI 



a. The higher plants and animals contain cells similar in struc- 



ture to entire unicellular organism, and like them exist- 

 ing in either the amoeboid, ciliated, encysted, or plas 

 modial condition 56 



b. Minute structure of cells : cell-protoplasm, cell-membrane, 



nuclear membrane, achromatin, chromatin 6 1 



c. Direct and indirect nuclear division .... ... 63 



d. The higher plants and animals begin life as a single cell, the 



ovum 67 



