阅读下文，回答各题。

纸船——寄母亲

冰心

                                                                                            我从不肯妄弃了一张纸，

                                                                                            总是留着——留着，

                                                                                            叠成一只一只很小的船儿，

                                                                                            从舟上抛下在海里。

                                                                                            有的被天风吹卷到舟中的窗里，

                                                                                            有的被海浪打湿，沾在船头上。

                                                                                            我仍是不灰心的每天的叠着，

                                                                                            总希望有一只能流到我要它到的地方去。

                                                                                            母亲，倘若你梦中看见一只很小的白船儿，

                                                                                            不要惊讶它无端入梦。

                                                                                            这是你至爱的女儿含着泪叠的，

                                                                                            万水千山求它载着她的爱和悲哀归去。

【注】本诗写于1923年冰心赴美留学的途中。