Sentence:  Other cultivators, however, advise "that the seed collected from a few turnips thus transplanted, should be preserved and sown in drills, in order to raise plants for see for the general crop, drawing out all such as are weak and improper, leaving only those that are strong and which take the lead; and that when these have <WSD>appled</WSD> or formed bulbs, to again take out such as do not appear good and perfect, as by this means turnip seed may be procured, not only of a more vigorous nature, but which is capable of vegetating with less moisture and which produces stronger and more hardy plants. 
Meaning of the word marked with <WSD> tags:  To form buds.