THE SECRETARY'S PORTFOLIO. 457 



violaccii ''both lots grow cxtreinely crowded ; the crossed were twice as tall as 

 the self-fertilized." Other examples of a similar iiaturo arc ,2;ivcn in the book. 

 Mr. Darwin, in volume II. of his Animals and IMants under Domestication 

 says, '' It is important that the two lots struggle with each other, for if sown 

 with jdenty of room and good soil, there is often but little difference in their 

 growtli.*" In other words the self-fertilized are more easily overcotne by 

 surrounding obstacles. Like pampered animals, they cannot endure great 

 hardships. In cultivating plants on the farm and garden in many cases they 

 are grown so close as to crowd each other. If so, seeds of crossed plants arc 

 generally the best, and most profitable to sow. 



EFFECT OF LOCALITY. 



Another fact mentioned in the case of EsclioUzia is not a lone instance. In 

 South America the self -fertilized ilowers are sterile, while if seeds are sown in 

 England the self-fertilized plants are the most productive and do the best. 

 All these things show the great need of many more experiments, and the dan- 

 ger of drawing conclusions too hastily from limited experience. As Darwin 

 says, " The fertility of a plant is a most variable clement, depending on its age, 

 health, nature of the soil, amount of water given and tempi-rature to whicli it 

 is exposed." To some extent we are groping in the dark. We do not know 

 all the conditions about any one experiment. 



Mr. llenslow brings up another point which should demand the careful atten- 

 tion of men of science, ^lany of our worst weeds are self-fertile. In a large 

 majority of cases weeds are foreign invaders — natives of other countries, but 

 this is not the case with all weeds. In some cases, the superior vigor of for- 

 eign weeds may be, and doubtless is to some extent due to a change of location. 

 Why do our weeds thrive so well? The tallest cabbage plants are not always 

 the best. In his experiments Mr. Darwin cut down and weighed the fully- 

 grown plants. Six self-fertilized plants of the third generation when they had 

 formed heads weighed 143.25 ounces; six plants from pollen of fresh stock 

 weighed G49 ounces. That is, the six "crossed plants averaged 108. IG ounces, 

 whilst the six finest self-fertilized plants averaged only 23.7 ounces, or as 100 

 to 22." Here again, we see an "enormous benefit" in favor of crossing a 

 variety with foreign stock of the same variety, which had grown for a few years 

 under different conditions. 



DIFFERING RESULTS. 



The scarlet runner bean ( Phaseolus muUiJiorus), in one case when covered 

 up yielded about one-third and in another case about one-eighth "of the num- 

 ber of pods which the same number of uncovered plants growing close along 

 side produced. This lessened fertility was not caused by any iujury from the 

 wet," as some of the protected Ilowers were artificially fertilized and produced 

 well. Dr. Ogle had tried a similar experiment with a total failure of fruit 

 when the Ilowers were protected. Phaseolus vulgaris, a closely related species, 

 proved highly fertile when insects were excluded. In England the varieties of 

 the sweet-pea rarely or never cross when grown near each other. This may not 

 be true in other places, as in Italy "it is the fixed opinion of gardeners there 

 that the varieties do intercross," that they cannot be kept pure unless protected 

 or sown in separate places. Let every person take warning from such examples 

 aiid not draw hasty conclusions from one illustration or experiment, or the 

 behavior of a single specimen. In some place a man does not see any bees 

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