1877.] 



103 



{Lyman. 



to time sends out side branches from points below the tip. Dicho- 

 tomy (the only growth that concerns Astropliytons) may have several 

 types. 1. The shaft may split in two equal halves; these in four; 

 the four in eight; the eight in sixteen, and so on. And if the dis- 



TABLE I. 



+» a a a s a 



- ' CO S CO ^ CO ^ CO 



■Sa .«a -sa .a a. 

 ^£ ©.a ©^ ££ 



^j Number of forks of ^.a^-s Number of forks of «-j§ 

 B a branches in their order o§ qs branches in their order ^ a 

 pR g from main stem. g g from main stem. -g g 



,0 ,fi ■ ,3 H-fi 



2 



6 



19 



88 



113 



178 



12 

 1 

 2 

 5 

 4 

 1 



13 



11 



2 



6 



8 



16 



32 



10 



1 



4 

 10 



34 



49 



9 



2 



8 



30 



40 



8 



1 



4 

 16 



21 



7 



2 

 8 



10 



6 



1 

 4 



5 



5 



2 

 2 



4 



1 

 1 



3 



11th 

 9th 

 7th 

 5th 

 3d 



10th 

 8th 

 6th 

 4th 

 2d 



3 



1 

 1 



4 



2 

 2 



5 



1 



4 

 5 



6 



2 



8 

 10 



7 



1 



4 



16 



21 



8 



2 

 8 



31 



41 



9 



1 



4 



14 



61 

 SO 



10 



2 



8 



26 

 68 

 108 



11 



1 

 1 



16 



28 

 35 



81 



12 

 2 



7 

 9 



18 



4 



5 



39 



93 



227 



368 



And forks of left side 178 



Total forks in one half an arm (right stem) 546 



• Astro phy ton Agassizii (see plate 5) table to exhibit the number of forks 

 in one stern (or one half an arm). Thus, the 2d fork of the arm, on the 

 right side of this right hand stem has, in its development 227 forks in- 

 cluded between the 2d and 12th forks as counted from the disk. Such a 

 stem is formed by the strong prongs of the successive forks. See plate 7, 

 fig. 3.) The total forks of the main stem and of its branches, on the right 

 and left being 546, the entire number of forks for the five arms would be 

 5,465 (in the same proportion) and the number of terminal twigs 5,470. 



tances between the forks are everywhere the same, there results 

 the perfect type of equal forking (Plate 7, fig. 6), a symmetrical fig- 

 ure corresponding to Winthrop's theory of branching. 2. When the 

 shaft splits or forks, it may form two prongs or branches of different 

 size ; one strong, the other weak. If the weak prong in consecutive 

 forkings is on opposite sides, alternating right and left, and the dis- 

 tances between the forkings are equal ; and if the strong prongs keep 

 the same direction and make together a straight line, there results a 

 figure with a straight central shaft which imitates an axial growth. 

 It may be called equal alternate straight forking , x and is illustrated by 



1 Dichotomie sympodique heligoide : Sachs, Traite" de Botanique. pp. 217, 219, 



