ON HYBRIDIZATION AMONGST VEGETABLES. 



83 



under different circumstances, because in different positions they 

 will have to contend with other difficulties and other rivals for 

 the occupation of the soil. I consider a due quantity of moisture, 

 without excess or deficiency, to be the main requisite to every 

 plant which has peculiar local affections, premising that it must 

 have space, unincumbered by stronger rivals that would over- 

 power it, and a suitable temperature. I have found a blue 

 Statice growing alofc in solid stone at the back of Portland island, 

 and elsewhere on the brink of a runnel in a saltmarsh ; I have 

 found Gentiana verna on the firm turfy brow of the St. Gothard, 

 and in the flooded marshes at the head of the lake of Thun. 

 The clouds and the sea-spray and fog furnished in the high posi- 

 tion that incessant moisture which those plants demanded, and 

 which the rival grasses found to be superabundant for their use 

 and injurious to their vigorous growth. 



To return to C. laevigatus : one of two views must be adopted, 

 either that schist, in a position where it receives a certain degree 

 of moisture under a certain temperature, is essential to enable a 

 variation of the genus Crocus which originated in such a posi- 

 tion to reproduce and maintain itself against all intrusion, or 

 that the like data tend to produce a similar variation in different 

 insulated spots ; but it is not easy to suggest a satisfactory reason 

 why such an indisposition to intermix should exist in a genus 

 which branches into so many local species with so much general 

 conformity both of habit and aspect. It has sometimes occurred 

 to me, that the variations produced by circumstances of poverty, 

 where the plant exists by superior powers of endurance, become 

 more fixed than those which arise from luxuriance. Crocus 

 seems to me to live in a state of constant mountain warfare, 

 avoiding the presence of powerful rivals ; Narcissi shoot both 

 early and vigorously, and usually domineer over the grasses, &c, 

 in the position they choose. The attempt to cross Crocus vernus 

 with other species led to some interesting observations. Plants 

 thereof were taken up and potted at the flowering season for 

 that purpose. I found that no excision, however deep, of a 

 flower that had expanded itself, and of which the pollen was set 

 free before it was taken up, could prevent the underground 

 germen within the sheaths of the plant from perfecting its seed 

 in due time. The fertilization had taken place and could not be 

 arrested. On the other hand, no application of its own pollen 

 would fertilize a flower after the transplantation ; the check 

 received prevented the fertilization; prevented, as I believe, the 

 plant from supplying that which the pollen required to enable it 

 to elongate its tubes. But a further remarkable circumstance 

 was observed. The roots so potted were plunged in a sand-bed, 

 that they might be ready for the next year's operation without 



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