Wooiiniffe-Pcacock : Floral Competition and Cycles. 415 



unused macadamised road or ' floor ' of a clay pit, or natural 

 slip on the face of the Neocomian escarpment, has neither con- 

 dition named. Nevertheless the annuals and biennials of tilth 

 soon seize on the unoccupied space in all such places, and 

 flourish for their allotted number of seasons ; till they are 

 thrust aside by strong"er g-rowing, deeper rootingf species. Room 

 to g-row according to their peculiar requirements, is the first 

 condition of plant life. It appears, too, that annuals, on account 

 of their limited root system want more air and soil space than 

 perennials in proportion to their leafage ; or in other words, 

 monocarps are more exacting in the circumstances of their 

 hurried growth cycle than polycarps. The (i) mechanical and 

 (2) chemical state of the soil — the two conditions, named above 

 in other words — are further ' helps and aids ' which annuals 

 always take full advantage of. The better the soil conditions, 

 too, the more rapidly are the annuals supplanted by perennials, 

 and the briefer their stay. These two conditions come, how- 

 ever, a long way after the all important requirement of freedom 

 from competition, and the moisture question certainly lies 

 between them. 



Poa annua, of our g^arden footpaths, proves how little is 

 required by annuals except space and moisture. I only once in 

 my life saw a crop of wheat actually growing which yielded 

 6^ quarters per acre. The seed had been specially selected, and 

 the soil was in the highest state of fertility ; the resulting crop 

 was so long and thick that the soil below was absolutely bare. 

 Six weeks from the^day the cereal was cut, a flock of sheep were 

 g"razing on the finest and purest crop of Poa annua I have ever 

 seen ! The conditions in this case were purely artificial, so 

 another instance shall be g"iven. Several years ago an ash tree, 

 standing in an old pasture, was uprooted in a heavy gale. In 

 its fall it rent the ground for three yards each away. A number 

 of annuals took possession of the torn surface at once, and vied 

 with one another in productivit)' for a time, as is their wont. 

 Amongst others were I'eronica arvensis, Laniiuni pui-pureum, 

 Se?ieclo vulgaris, and Bromus sterilis. 



The soil, as is usual in old pasture land, was exceedingly rich, 

 and the turf quickly asserted its former supremacy. Watching- 

 the result was worth the continual observation such a case re- 

 quires. For some seasons the four species named have been 

 driven from their former foothold, and have grown in the trifling- 

 material which, after the sun, wind, and rain of all seasons, still 

 clings to the roots of the overthrown stump. There, two feet 



1906 December i. 



