Marine Groves and Gardens 137 



An acute observer once pointed out that there seems 

 to prevail a natural rule to the effect that as an organ 

 becomes more highly specialized or as plant and animal 

 life becomes more advanced in development, the ability 

 to regenerate injured tissues or lost parts becomes in- 

 creasingly diminished. For instance, in higher animals 

 the stomach, a primitive organ, can undergo consider- 

 able mutilation and recover its pristine vigor, but the 

 slightest damage to the more specialized kidneys is 

 practically irreparable. Then, again, the facility with 

 which low^er animals, from the sponges to the crus- 

 taceans, can grow lost parts, when compared wath that 

 of the vertebrates, is another case in point. Well, at 

 any rate, w^hatever may be the value of this rule in its 

 application to higher forms, it is certainly true so far 

 as it Is reflected by the seaweeds. With some doubtful 

 exceptions, red algs cannot give rise to new individuals 

 if the fronds are detached from the base. In other and 

 lowxr forms, however, growth constantly proceeds re- 

 gardless of an injury of this sort. This method of cell 

 reproduction, known as vegetative multiplication, is 

 carried to an extreme by many green seaweeds. A 

 good example is Ulva. When it is In the growing stage 

 It can be torn into any number of parts, and each one 

 will continue to enlarge into a conspicuous frond. 



The seashore is the great evolutionary threshold of 

 both plants and animals. I have already mentioned 

 the fact that some of the marine algae are learning to 

 live out of the water; but there are, on the other hand, 

 not a few land plants which have taken to the sea. x\nd, 

 curiously, these for the most part are represented by 

 the higher, or flowering, forms. This reversion to 



