登陆注册
4707200000136

第136章

I. pages 412 et seq.) tried to show that garden-races have been produced only from spontaneous types which occur in a wild state or from sub-races, which the breeder has accidentally discovered but not originated. In a small number of cases only has de Vries adduced definite proof. On the other side we have the work of Korschinsky (Korschinsky, "Heterogenesis und Evolution", "Flora", 1901.) which shows that whole series of garden-races have made their appearance only after years of cultivation. In the majority of races we are entirely ignorant of their origin.

It is, however, a fact that if a plant is removed from natural conditions into cultivation, a well-marked variation occurs. The well-known plant-breeder L. de Vilmorin (L. de Vilmorin, "Notices sur l'amelioration des plantes", Paris, 1886, page 36.), speaking from his own experience, states that a plant is induced to "affoler," that is to exhibit all possible variations from which the breeder may make a further selection only after cultivation for several generations. The effect of cultivation was particularly striking in Veronica chamaedrys (Klebs, "Kunstliche Metamorphosen", Stuttgart, 1906, page 152.) which, in spite of its wide distribution in nature, varies very little. After a few years of cultivation this "good" and constant species becomes highly variable. The specimens on which the experiments were made were three modified inflorescence cuttings, the parent-plants of which certainly exhibited no striking abnormalities. In a short time many hitherto latent potentialities became apparent, so that characters, never previously observed, or at least very rarely, were exhibited, such as scattered leaf-arrangement, torsion, terminal or branched inflorescences, the conversion of the inflorescence into foliage-shoots, every conceivable alteration in the colour of flowers, the assumption of a green colour by parts of the flowers, the proliferation of flowers.

All this points to some disturbance in the species resulting from methods of cultivation. It has, however, not yet been possible to produce constant races with any one of these modified characters. But variations appeared among the seedlings, some of which, e.g. yellow variegation, were not inheritable, while others have proved constant. This holds good, so far as we know at present, for a small rose-coloured form which is to be reckoned as a mutation. Thus the prospect of producing new races by cultivation appears to be full of promise.

So long as the view is held that good nourishment, i.e. a plentiful supply of water and salts, constitutes the essential characteristic of garden-cultivation, we can hardly conceive that new mutations can be thus produced. But perhaps the view here put forward in regard to the production of form throws new light on this puzzling problem.

Good manuring is in the highest degree favourable to vegetative growth, but is in no way equally favourable to the formation of flowers. The constantly repeated expression, good or favourable nourishment, is not only vague but misleading, because circumstances favourable to growth differ from those which promote reproduction; for the production of every form there are certain favourable conditions of nourishment, which may be defined for each species. Experience shows that, within definite and often very wide limits, it does not depend upon the ABSOLUTE AMOUNT of the various food substances, but upon their respective degrees of concentration. As we have already stated, the production of flowers follows a relative increase in the amount of carbohydrates formed in the presence of light, as compared with the inorganic salts on which the formation of albuminous substances depends. (Klebs, "Kunstliche Metamorphosen", page 117.) The various modifications of flowers are due to the fact that a relatively too strong solution of salts is supplied to the rudiments of these organs. As a general rule every plant form depends upon a certain relation between the different chemical substances in the cells and is modified by an alteration of that relation.

During long cultivation under conditions which vary in very different degrees, such as moisture, the amount of salts, light intensity, temperature, oxygen, it is possible that sudden and special disturbances in the relations of the cell substances have a directive influence on the inner organisation of the sexual cells, so that not only inconstant but also constant varieties will be formed.

Definite proof in support of this view has not yet been furnished, and we must admit that the question as to the cause of heredity remains, fundamentally, as far from solution as it was in Darwin's time. As the result of the work of many investigators, particularly de Vries, the problem is constantly becoming clearer and more definite. The penetration into this most difficult and therefore most interesting problem of life and the creation by experiment of new races or elementary species are no longer beyond the region of possibility.

同类推荐
热门推荐
  • 球童

    球童

    莫洋,你为什么要装作不会打篮球?这句话是在大一第六个礼拜的体育课上,陈磊在莫洋的耳边轻轻说的。莫洋和陈磊选的都是羽毛球班,当时的莫洋一如往常,在老师宣布自由练习之后便一屁股坐在了场边,而陈磊则走到他的边上蹲了下来。莫洋直视着陈磊的小平头脑袋,说你见过我打篮球么?陈磊摇摇头说没有。莫洋说那你干嘛说我会打球?我不会。陈磊说,不可能,那天我亲眼看见了,你从二号场地的羽毛球网上跳了过去,这么好的弹跳,很少是天生的,要我说,你肯定是经过了严格的训练。
  • 冒牌老婆很神秘

    冒牌老婆很神秘

    新文:大爱晚成,卯上天价老婆http://m.wkkk.net/a/998094/*传说:佟庭烽是个凉薄的男人,他是巴城第一少,他尊贵,他绅士,他深不可测,他在巴城乃至全国都有着呼风唤雨的能力,也是无数未婚女子梦寐以求的丈夫人选。六年前,他二十四岁,一朝失足,随即奉子闪婚。婚后,夫妻形如陌路。六年后,一场空难,身份互换之下,宁敏替代韩婧成为了他的冒牌妻,不为他的钱和权,只想尽快离婚,借他老婆的身份光明正大的重新活一场。他们以为她还是那个柔弱可欺的韩婧,却不知她早已不是她,面对小姑的刁难,婆婆的为难,前男友的步步追缠,以及丈夫的冷淡……她难道就该逆来顺受吗?绝不。逆袭之后:小姑哭了,婆婆呆了,前男友对她彻底着迷了,而丈夫,霸着她不肯放了。一“佟大少,愿赌服输,请签字离婚……”当她递上离婚协议,要求履行约定时,男人微微而笑:“签字可以,先说明自己的身份,一次性交代清楚了,咱们好去另外注册领证!”宁敏惊呆:啥,这男人什么时候知道她是冒牌的了?二某一日,佟大少问妹妹:“怎么样才能哄你嫂子开心?”“给她最想要的东西!”“那可不行!”“哥哥什么时候变的这么小气?你要不给,怎么取悦芳心?遭了嫌的佟大少直皱眉:“她最想要的是:离婚和儿子。我真要是给了,她保准拍拍屁股溜走!”妹妹:“……”哥,你运气真背,穷尽三十年才喜欢上一个,人家居然不稀罕你。三酒醒后,宁敏很想找个地方把自己给埋了,却被拎了回去。“我不是故意的!”面对人家身上那一片青青紫紫,她举双手发誓。“不管有意还是无意,你强了我是事实!”有人得了便宜还卖乖:“你得对我负责到底。婚不离了!”宁敏立马急叫:“那怎么行,你答应过的。”“我反悔了!再说,你又不是韩婧,最重要的是:我太太因你而亡故,你得赔我一个太太,现在又染指了我,这个责任你非负不可!”“……你这是坑我!”“嗯,你才知道呀!”男人扬眉笑:“我这也是没办法,儿子说的。他要妹妹!不如,我们造一个出来?”*宁敏一直在想一件事:六年前令她怀孕的男人,究竟是谁?她的女儿继承的又是谁的DNA?男朋友和她现任丈夫,到底哪一个才是她女儿的亲生父亲?*
  • 心爱的树

    心爱的树

    本书收入蒋韵的中篇小说《心爱的树》《朗霞的西街》《晚祷》《完美的旅行》《行走的年代》等。“失去、生命悲情、苦难”这是蒋韵几十年来不断书写的文学母题。
  • 混在大马的日子5

    混在大马的日子5

    出国留学的去向要视留学生的目的而定——公派留学并且将来想成为教授的,英国是最佳选择;想学业有成外加移民的,自然是去美国,澳洲,加拿大;想以留学的名义打工为国家赚取大量外汇给社会主义建设添砖加瓦的,日本是首选;对于想趁着青春年少游山玩水,在自己的生命中留下些甜蜜回忆,再顺便镀层金的中国“游学生”们,风光秀丽的马来西亚实在是个不错的地方。马来西亚最大的私立学院——如来学院(这真的不是一间佛学院!)以‘爱玩’为第一主人公的‘有志青年们’的故事,嬉笑谩骂,待看人生。
  • 侠岚之青春时光

    侠岚之青春时光

    他本是一个富家子弟,却因为一次事故失去了记忆过起了平凡人的生活。当他恢复记忆再次回到家族中,会引起怎样的争斗呢......
  • 开会开不好,怎么做公司领导

    开会开不好,怎么做公司领导

    现代社会,会议是每一个职场人必须经历的活动,每个场合都存在着各种目的和各种形式的会议,政府机关和事业单位有政工会议和业务会议,学校里有学生参加的班会和家长参加的家长会,企业里的会议更是种类繁多,销售会、动员会、招商会……数不胜数。客观、公平和正确的认知会议,掌握开会的技巧和方法是必须的。
  • 百位世界杰出的发明家(下)(世界名人成功启示录)

    百位世界杰出的发明家(下)(世界名人成功启示录)

    人类的未来充满了希望,明天的世界令我们无比期待。从历史中汲取知识,感悟人生,追求真理,是每个生活在21世纪的现代人的价值取向。在无比灿烂的历史星空中,众多世界杰出人物犹如明烁夺目的明星,让历史的时空如此地浩瀚,并给后人留下了一份极其珍贵的文化遗产与智慧结晶。期望本书能让广大读者,尤其是青少年朋友们,从世界杰出的人物身上,学习与借鉴人生的智慧,创造卓越的人生。
  • 宇宙末日之惊天决战

    宇宙末日之惊天决战

    公元三千年,地球进入未来纪,两颗不规则的巨型小行星同时分别撞向了地球南北两极,引发地球末日。剩存的地球物理学家蓝科博士带领他的五个学生利用高科技技术暂时阻止了地球的爆炸解体。同时,无垠的宇宙星空在超级黑洞的吞噬下进一步萎缩变形,拥有超能量的外星巨人欲趁机称霸宇宙,以肖飞影为首的拯救地球青春无敌小分队化身铁甲战士同外星巨人展开了一场事关宇宙生死存亡的大决战。
  • 广陵妖乱志

    广陵妖乱志

    本书为公版书,为不受著作权法限制的作家、艺术家及其它人士发布的作品,供广大读者阅读交流。汇聚授权电子版权。
  • 老公,你太无赖

    老公,你太无赖

    夜色朦胧月如钩。繁华的大都市霓虹灯闪烁着,街上人来人往,络绎不绝。昏暗的酒吧灯光闪烁,里面响起了动感的音乐,舞池里面的男女不停的扭动着身体,兴奋得直尖叫着。吵死了,掏了掏耳朵,真想一个个拖出去给枪毙了,跳就跳,鬼吼鬼叫个毛线!蓝若然坐在高脚椅子上一个人喝着闷酒,幽暗的灯光洒在她的身上,映照出迷人的线条的还有精致的面容。不施粉黛却依旧是美得……