SYNOPSIS 483 



J'AGE 



38. Equisetutn. 



Sporangia borne on sporophylls arranged in cones : 

 spores homomorphic : prothalli dimorphic (male and 

 female) 434 



39. Salvinia. 



Spores dimorphic : microspore produces vestigial male 

 prothallus : megaspore produces greatly reduced female 

 prothallus 438 



40. Selaginella. 



Microspore produces unicellular prothallus and multi- 

 cellular spermary, both endogenously : female prothallus 

 formed in megaspore and is almost endogenous : embryo 

 provided with suspensor 442 



41. Gymnosperms. 



Cones dimorphic (male and female), with rudimentary 

 perianth : no sperms formed but microspore gives rise to 

 pollen tube, nuclei in which are the active agents in fer- 

 tilisation : single megaspore permanently enclosed in each 

 megasporangium : female prothallus purely endogenous : 

 embryo (phyllula) remains enclosed in megasporangium 

 which becomes a seed 447 



42. 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 synergidoe : formation of prothallus re- 

 tarded until after fertilisation 461 



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 organisms, 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, nuclear sap, chromatin 62 



c. Direct and indirect nuclear division 6<j 



I I 2 



