42 PRINCIPLES OF PLANT-TEBATOLOGY. 



inflorescences there is, if not a complete absence, a 

 mucli greater dearth than is normally the case, of 

 lateral inflorescences. The two phenomena are thus 

 obviously correlated, the one being the result of the 

 other. Yet, bearing in mind the definition of " fascia- 

 tion " given in an earlier section, it would, on this 

 definition, not be correct to say, as, for example, in 

 the instance frequently seen in the spear thistle 

 {Gardmis lanceolatus), that the fasciated terminal head 

 was due to fusion of the lateral heads with the 

 terminal one, for there is no evidence of any such fusion. 

 Rather we should say that the fasciated head is the 

 equivalent of the two categories of heads (terminal and 

 lateral). The main head, with the axis bearing it, 

 has, for one cause or another, started in a condition 

 of excessive robustness and vigour, and this has 

 involved the absence of sufficient superfluous vigour 

 and nourishment for the formation of the normal 

 number of lateral heads ; hence, in one sense, it is true 

 that these have become congenitally absorbed or fused 

 into the main head and tend to become separated out 

 again at the apex (so to speak). 



It is this primary congenital " absorption " of in- 

 dividuals which might, under other conditions of the 

 environment or of the plant's constitution, have been 

 formed separately, together with their subsequent 

 separation, or partial separation, at the apex of the 

 structure so formed which gives rise to the phenomenon 

 of fasciation wherever, in the vegetable kingdom, it 

 may be found. For example, it might happen that an 

 ovum of abnormal development, equal, perhaps, in size 

 to two ordinary ova, is formed in the embryo-sac. If 

 this ovum divides completely into two, twin-embryos 

 are the result; if it does not so divide the result of 

 fertilization would be an abnormally robust embryo 

 producing a plant with a tendency to fasciation. The 

 idea of " fusion " is only permissible here in the sense 

 that, where a single abnormally large ovum was formed, 

 two ova of normal size might have been formed. The 



