CHAPTER VII 

 THE ARCHEGONIAT^; MUSCINEJE 



THE Algae are typically aquatic plants, and even those forms 

 which are adapted to life out of the water can vegetate only when 

 an abundant water supply is present, and remain dormant when the 

 supply is withdrawn. These plants reach their most perfect devel- 

 opment in the sea, where the water supply is constant, and the 

 highest expression of the algal type is seen in the large Red and 

 Brown Algae. 



From the much simpler fresh-water Green Algae another group of 

 plants has been derived which has far outstripped all other com- 

 petitors and developed the most perfect of all plant-structures. 

 These are the terrestrial green plants which at present are the pre- 

 vailing plant-types. The lowest of these terrestrial plants, the 

 Archegoniatae, show unmistakable evidences of* their aquatic origin, 

 and although no existing Green Algae can be pointed out as the 

 direct ancestors of the land-plants, still there is strong evidence 

 that the lower Archegoniates, the most primitive of the terrestrial 

 plants, have arisen from forms allied to the existing Chlorophyceae. 

 On the whole, the Confervaceae offer the closest analogies with the 

 Archegoniates, and of these the genus Coleochaete shows the nearest 

 affinity, although the character of the reproductive organs in the 

 Characeae also gives some suggestions of the archegoniate type. 

 The Archegoniatae include the Mosses and Ferns and their allies. 



The substitution of an aerial for an aquatic environment was no 

 doubt very gradual, and there are still some forms among the Green 

 Algae and lower Archegoniates which show how this may have come 

 about. The advantages of being able to grow with a diminished 

 water supply are obvious. Most fresh-water Algae are subjected to 

 destruction by the drying up of the shallow ponds in which they 

 grow, and their vegetative period may be very short. To provide 

 against this there are developed the various forms of resting-spores, 

 which remain dormant until the supply of water is renewed. A 

 few forms, like Botrydium and some species of Vaucheria, grow on 

 the mud left by the receding water, but their growing period 

 is entirely dependent upon the - length of time during which the 

 mud remains moist, and they also produce resting-spores at the end 

 of their short vegetative existence. 



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