PRINCIPLES OF PLANT-TERATOLOGY. 



undivided while the upper is separated into two 

 similar parts, represents at once the simplest case of 

 fasciation in existence and also the phenomenon 

 which most easily and clearly explains it, illustrating 

 as it so well does the result of the compromise 

 between the two tendencies towards unification and 

 separation respectively. It is a by no means un- 

 common phenomenon for two embryos or young 

 seedlings to appear more or less intimately fused 

 together. De Candolle figures cases of this sort in 

 the sun-spurge (Euphorbia Helioscopia) and Sinapis 

 ramosa in which the fusion occurs from the insertion 

 of the cotyledons downwards. In the phenomenon as 

 observed in Eremostachi/s laciuiata, the union was in 

 the region of the primary, node only, the cotyledons 

 and radicles being quite free : a veritable Siamese 

 twins of the vegetable world ! (PI. IX, fig. 4). Morris 

 describes a very similar case to this in Widdringtonia 

 cupressoides. 



All cases of dichotomy in Angiosperms represent, 

 therefore, imperfect twin -formations ; one could even 

 apply the same statement to all normal cases of 

 dichotomous branching in Cryptogams. Fasciation is 

 the imperfect formation of a number of offspring 

 (multiplets) by partition, and is a result of the com- 

 promise established between the forces making for 

 unity and fission respectively. The fasciated shoot is 

 a unity, a single individual structure, as is clearly 

 evidenced by its homogeneous cylindric base. Its 

 expansion in one plane of the diameter proportionately 

 to the increase in stature is due to the tendency on 

 the part of the shoot to dichotomize, this being equally 

 balanced and neutralized at every moment by the 

 opposite tendency, viz., that to cohere as a unity ; this 

 alone is the vera causa of the ribbon-growth with 

 which we are so familiar.* 



* In an interesting case of this in Sterculia alata from Wallich's collec- 

 tion, the collector says of it : " Two embryos seemingly from one nucleus, 

 soldered together, with only two cotyledons to both conjointly above which 

 separation has taken place naturally." 



