298 Bryophyten. — Floristik etc. 



The archegonium proper is initiated in the manner usual among 

 the Bryophytes. In the terminal cells three oblique walls cut off 

 three peripheral segments and originate the primary axial cell 

 within, which on division gives rise to cover cell and central cell. 

 The Cover cell is relatively inactive and cutts off no basal segments. 

 The central cell on division forms the primary neck canal cell (the 

 mother cell of the neck canal row) and the primary ventral cell. 



The growth of the neck canal row is intercalary, the cells divi- 

 ding in almost any order. 



The primary ventral cell divides late into ventral canal cell 

 and Qgg. 



The growth of the wall cells of the archegonium is intercalary. 



The mature archegonium has 8 or 9 canal cells. 



The breaking down of the canal row may begin at any point, 

 is frequently acropetal, but never involves the ventral canal cell. 

 The ventral canal cell is persistent, behaves for a time exactly as 

 does the egg, but normally disintegrates just before the archego- 

 nium opens for fertilization. 



Abnormalities, such as double venters, multiple eggs, etc, are 

 of common occurrence. 



The general conclusion is that the archegonium of Sphagnum 

 subsecundum is synthetic. The stalk, the thick venter, and the 

 comparatively slender twisted neck are moss characters; the relati- 

 vely inactive cover cell, the intercalary growth of the archegonium, 

 and the low number of canal cells are hepatic characters as we 

 know them today, Jongmans. 



Brown, H. P., Growth studies in forest trees. 2. Pinus 

 Strobus L. (The Bot. Gazette. LIX.p. 197— 241. PI. 13, 14. 2 Fig. 1915.) 



The present paper is the second of a series presenting the re- 

 sult of studies of growth in forest trees. The investigations are 

 planned with a twofold purpose, namely to clear up some disputed 

 points regarding the formation of annual rings and to outline the 

 laws of growth in trees. The results of the studies of Pinus Strobus 

 L. are presented in this paper. 



The Winter condition of the secondary cortex and cambium of 

 white pine is similar to that of Pinus rigida. The marked differen- 

 ces which occur between the mature bark of white pine and pitch 

 pine are occasioned by changes which take place in the outer 

 cortex (periderm). 



The cambium varies both in number of cell layers (2—10) and 

 thickness in different parts of a tree. It is smallest in both these 

 respects in the twigs and young branches, and increases gradually 

 in dimensions from the apex downward, until that point is reached 

 in the hole where the last annual ring is the thickest. Thereafter, 

 the decrease in the diameter is not proportional to the fallingoffin 

 the diameter of the last formed ring. 



Phloem development continues until late in the autumn, much 

 longer than xji^lem development. Sieve tubes in all stages of for- 

 mation occur between cambium and fully formed phloem, The sea- 

 sonal growth of phloem exhibits little or no compression as late as 

 October first. Subsequently contraction occurs, due to the extreme 

 cold temperatures of winter. All the seasonal growth of ploem is 

 crushed with the exception of the last 6 or 8 transitional tracheids. 

 Compression is greater in the crown than below. 



