April. 1919.] ^'^^'^ GERMINATION AND DEVELOPMENT. 87 



stant irrigation on the coast, while on the other calm and 

 warmer regions the vegetation may be destroyed by heat during 

 summer. 



On our coasts, species of Wildemania grow luxuriously 

 during summer in the north Kuriles and very poorly in other 

 seasons. In middle and sourthern Japan, there are 4-5 summer 

 months in a year when none of healthy fronds of Porpbyra 

 can be seen. 



On April 6 this year, I took some fronds with mature 

 carpospores growing on the experiment block and carried back 

 to the University Laboratory at Sapporo. They were carried 

 in a glass jar filled with filtered sea-water, and were transfer- 

 red into into a large beaker. The fronds were taken out of 

 the water twice a day as to imitate the ebb tides^\ Within a 

 few days I could plainly perceive a light purplish hue on the 

 bottom of the beaker. It was ascertained that the ripe car- 

 pospores have sunken there in a considerable number as to 

 give the colour. The spores stuck to the glass surface with a 

 gelatinous matter and were not disturbed by certain degree of 

 movement of the water. The fronds were now taken away out 

 of the apparatus. 



The water in the beaker was emptied twice a day to 

 imitate the tide ebbings. After carrying on this experiment for 

 four days, I noticed a good number of spores change their 

 colour, apparently undergoing to decay. The beaker was re- 

 placed with other one with healthy spores in it and the arti- 

 ficial tide ebbings were abandoned. The stopped. The spores 

 in the bottom of the beaker remained constantly in the 

 water. 



The beaker was placed in a well-lighted corridor, but not 

 under direct sun light. The temperature of the water in the 

 beaker ranged between 6° C and 14° C. This temperature 

 nearly agrees with that of the natural habitat of the plant. 

 The following table shows the temperature of the surface water 

 at Takashima near Oshoro. 



1) HinteJ by Miss Baker's paper : On the Brown Seaweeds of the Salt Marsh 

 (Linnean Society's Journal Botany. Vol. XL, 1912). 



