138 H0FME1STER, ON 



16, 17).* This circumstance justifies the conclusion that at 

 the commencement of the formation of a lateral branch a 

 portion of the apical cell-cavity, which, under ordinary cir- 

 cumstances, becomes the primary cell of a leaf, is applied to 

 the formation of the rudimentary cell of the branch. It is 

 probable that the formation of the branch takes place earlier 

 than that of the leaf which stands at the same elevation in 

 the ascending line of the spiral of the phyllotaxis. Assuming 

 this to be so, the process can hardly be viewed otherwise 

 than as a separation from the four-sided terminal cell, of an 

 irregularly shaped cell of the second degree with a three- 

 sided apical surface ; after which separation the apical cell 

 divides by a septum which is parallel to one of the shorter 

 sides of the apical surface, and is inserted in the angle 

 formed by the oldest lateral wall of the apical cell with one 

 of the lateral surfaces of the rudimentary cell of the branch. 

 This latter division would restore the apical cell to its three- 

 sided pyramidal form. The direct observation of this pro- 

 cess can only be accidental. Indications, however, of such 

 a state of circumstances clearly exist in the occasional 

 occurrence of very slender apices (of stems), whose conical 

 end extends far above the last leaf-rudiment which is visible 

 in profile, so that in the optical section of the naked cone 

 two superposed cells of the second degree can be distin- 

 guished on one or on both sides. f 



Most lateral branches ramify soon after their formation. 

 Schimper (1. c, p. 30), judging from the anatomical struc- 

 ture of the points of origin of perfect branches, concludes 



* In the ' Vergleichende Untersuchungen,' p. 62, 1 made use of an expression 

 which might lead to the belief that I considered the lateral branches as axile in 

 their origin. This arose from my having only had in view the relation of the 

 elementary cell of the lateral branch to the leaf below it. Schimper, at p. SO 

 of his work on Sphagnum, has rightly objected that, the position of the rudi- 

 mentary as well as of the perfect lateral branches is always at the side, near 

 the margin of the leaf which stands at the same elevation. 1 consider Schimper, 

 however, to be in error (1. c, p. 30) in supposing that certain oval (occasionally 

 stalked) cells, which are interpolated between each two moderately distant 

 leaves, and which are seated upon the outer surface of the stem, are to be 

 looked upon as the rudimentary cells of lateral branches. These cells are 

 nothing more than the young state of the bicellular hairs, with oval terminal 

 cells, which occur not unfrequently upon the stem of Sphagnum, and which 

 are figured by Schimper himself (pi. v, f. 2). 



f Such terminal buds have often been figured, for instance, by myself in the 

 'Vergl. Unters.' (pi. xiii, f. 1), and by Schimper (1. c., pi. iii, f. 2, 7). 



