Insectivorous plants / by Charles Darwin.

  • Darwin, Charles, 1809-1882.
Date:
1888
Catalogue details

Licence: Public Domain Mark

Credit: Insectivorous plants / by Charles Darwin. Source: Wellcome Collection.

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    least flourishing half of each culture was selected to he “ fed,” while the rest of the plants were destined to he “ starved.” The plants were prevented from catching insects for them- selves by means of a covering of fine gauze, so that the only- animal food which they obtained was supplied in very minute pieces of roast meat given to the “ fed ” plants but withheld from the “starved” ones. After only 10 days the difference between the fed and starved plants was clearly visible: the fed plants were of brighter green and the tentacles of a more lively red. At the end of August the plants were compared by number, weight, and measurement, with the following striking results :— Starved. Fed. Weight (without flower-stems) . . . 100 121-5 Number of flower-stems ..... 100 164-9 Weight of stems 100 231'9 Number of capsules 100 194-4 Total calculated weight of seed . . . 100 379'7 Total calculated number of seeds . . . 100 241‘5 These results show clearly enough that insectivorous plants derive great advantage from animal food. It is of interest to note that the most striking difference between the two sets of plants is seen in what relates to reproduction— i.e. in the flower-stems, the capsules, and the seeds. After cutting off the flower-stems, three sets of plants were allowed to rest throughout the winter, in order to test (by a comparison of spring-growth) the amounts of reserve material accumulated during the summer. Both starved and fed plants were kept without food until April 3rd, when it was found that the average weights per plant were 100 for the starved, 213‘0 for the fed. This proves that the fed plants had laid by a far greater store of reserve material in spite Of having produced nearly four times as much seed. In Kellermann and Yon Raumer’s experiments (loc. cit.) aphides were used as food instead of meat—a method which adds greatly to the value of their results. Their conclusions are similar to my own, and they show that not only is the seed production of the fed plants greater, but they also form much heavier winter-buds than the starved plants. Dr. M. Biisgen has more recently published an interesting paper * on the same subject. His experiments have the * “ Die Bedeutung des Insectfanges fur Drosera rotundifolia (L.),” ‘ Bot. Zeitung,’ 1883.