The following points highlight the three families under which cordaitales has been classified. The families are:- 1. Pityaceae 2. Poroxylaceae 3. Cordaitaceae. Family # 1. Pityaceae: Pityaceae is known only from trunks of wood and a few vegetative shoots. OccurÂring in the Devonian and the Lower Carboniferous, they comprise the oldest of the Cordaitales. Arnold (1947) is of opinion that [...]
In this article we will discuss about:- 1. Distribution of Cycas 2. Morphological Features of Cycas 3. Internal Structure 4. Reproduction 5. Economic Importance. Distribution of Cycas: It is the only genus of the family Cycadaceae, which is represented in India. It has got about 15 species (Sporne, 1965), 20 species (Willis, 1966) which are widely distributed in Eastern as [...]
In this article we will discuss about:- 1. Definition of Gymnosperms 2. External Features of Gymnosperms 3. Classification 4. Internal Structure 5. Reproduction 6. Affinities and Relationship 7. Evolutionary Significance. Definition of Gymnosperms: The term gymnosperms (gymnos = naked; sperma = seed) was introduced by Theophrastus in 300 BC to describe plants with unprotected seeds. According to Goebal gymnosperms are [...]