376 BOTANICAL GAZETTE [November 



asm 



of the embryo, arousing it to growth. He holds 

 that the action is not on the coats, and adduces as evidence the facts 

 that the seed coats are permeable to both water and compounds dis- 

 solved in it, and that a disorganization of the coats is brought about 

 only by long exposure to such agents as concentrated H2SO4. He 

 believes that the weak acids and bases used as stimuli could have 

 no effect on the coats, and that in nature the germination is brought 

 about by acid, formed in the decay of organic matter in ponds, which 

 acts upon the dormant protoplasm. 



I find that Fischer is entirely wrong in assuming, first, that the 

 protoplasm of these seeds is in a dormant stage; and, second, that 

 a chemical stimulus is necessary to bring aT)out germination. Like- 

 wise MxJLLER is wrong in assuming desiccation to be necessary for 

 the germination of the seeds of Eichhornia. I find that the embryos 

 of all seeds of w^atcr plants I have tested begin germination very 

 readily when the ordinary conditions for germination are furnished 

 them, and especially the one condition of sufficient water supply. 

 In an article already published,^ I have shown that cases of delayed 

 germination or entire failure to germinate are generally related to the 

 character of structures inclosing the embryo and not to dormancy of 

 its protoplasm- In the paper cited I mention certain species of Iris 

 that germinate only when the cap covering the embryo is removed, 

 although the structures are permeable to w^ater and the embryo 

 imbibes water until it entirely fills the cavity it occupies. The water 

 thus admitted is not sufficient to start growth, and the embryo lies 

 in this semi-saturated condition. It is onlv when the limits to water 

 absorption are removed that growth begins. Exactly the same thing 

 occurs with the seeds mentioned bv Muller and Fischer. Before 

 discussing this point farther some facts about the ripening and har- 



-nentioned in the table below must be stated. 

 The seeds of Alisma, Sagittaria, and Typha all ripen above water, 

 while those of Eichhornia and Potamogeton ripen under water, as do 

 the seeds of m^ny other water plants. The ripening under w^ater is 

 brought about by the flower stalks responding positively to gravity 

 soon after fertihzation. A large number of Jlichhornia seed stalks 



5 Crocker, Wm., R61e of seed coats in delayed germination. BoT, Gazette 

 42:265-291, 1906- 



