I 10 A NEW ZEALAND NATURALIST'S CALENDAR. 



Here gentle currents of wind, or perhaps minute semi- 

 aquatic insects (gnats, etc.), convey the pollen from flower 

 to flower. As soon as fertilisation has taken place the 

 ovaries begin to grow and develop, and at the same time 

 the stalk begins to twist itself up like a short corkscrew, 

 so that the fruit is ripened close down to the bottom of 

 the water, out of the reach of waves which might tear the 

 fragile stems to pieces. I do not think it at all likely that 

 either Ruppia or Zaniilchellla could grow in sea water, 

 but an allied plant has acquired the power, but at the 

 same time has lost the power of growing in fresh water. 

 This is the Zostera or "Sea Wrack," which, though not 

 found in Tomahawk Lagoon, grows in such abundance in 

 the harbour. The banks are covered with this slender 

 grass-like bright green plant, which is not a seaweed or 

 Alga at all, but a true flowering plant. Now, every tyro 

 in botany knows that flowering plants only produce seeds 

 when the pollen has been so placed on the stigma of the 

 pistil as to bring about fertilisation. But pollen is not 

 intended to be wetted, and as Zostera grows in the sea, 

 and is either always covered with water or is only exposed 

 at low tides, it has to produce its flowers in little water- 

 tight cases. It is thus always self-fertilised, and these 

 cases do not decay or open until the contained fruit 

 has set. 



As we wander round the lagoon, especially on its 

 northern side, we find great quantities of pondweed, 

 duckweed, and the pretty little red Azolla growing, the 

 first-named rooted in the mud and floating up its oval 

 brownish leaves on to the surface, the two latter floating 

 quite detached and sending down little roots to a depth of 

 nalf-an-inch or more. Duckweeds are the smallest of all 

 flowering plants. They have no distinct stem or leaf, but 

 the whole plant consists of a flat green expansion or frond, 

 seldom reaching a fourth of an inch long. In a cleft of 

 this little sheet of tissue there grows a cluster of most 

 minute flowers. Azolla is not a flowering plant, but is 

 allied to the ferns. Where these plants are found in such 

 abundance, other forms of life both vegetable and animal 



