308 The Philippine Journal of Science 1923 



There now remains but the discussion of the minute details 

 of pit structure and intercellular spaces to complete the pres- 

 ent investigation. Discussion of these has purposely been left 

 until the last since they required magnifications ranging from 

 one to two thousand, which were wholly unnecessary for the 

 remainder of the study. In the foregoing pages mention has 

 been made of the kinds of pitting that characterize prosen- 

 chyma and parenchyma, namely, the bordered and the simple 

 type, and this point should be borne in mind in order to under- 

 stand more clearly the prevailing relationships. It is assumed, 

 moreover, that the reader is familiar with the general details 

 of structure that characterize simple and bordered pits. 



The pitting of Parashorea is depicted in Plate 9 and exhibits 

 a surprising range of variation in form and size, which is in 

 part traceable to the type of element concerned and in part 

 to the angle of vision. Throughout, the pit cavities present 

 a punctate appearance, owing to the presence of granular or- 

 ganic material which, when a pit is seen in surface view, 

 suggests perforated pit membranes as reported by Jonsson 28 

 in certain Leguminosse, an illusion which is readily corrected 

 when the pits are seen in sectional view. Whether this organic 

 material is in the nature of a residue left behind following the 

 disappearance of the protoplasts in the cells concerned or is of 

 physiological significance can only be conjectured. A second 

 striking feature is the noticeable lack of tori in the membranes 

 of the bordered or semibordered pits, a condition that ap- 

 parently holds throughout the dipterocarp family. Even where 

 the pits are distinctly bordered and approach those of conifer- 

 ous wood, the middle lamella spanning the pit cavity presents 

 an even appearance without suggestion of thickening of any 

 sort. Parashorea wood is characterized by the total absence 

 of tori in the pit membranes. 



As seen in surface view the simple pits appear as circular, 

 oval, or polygonal areas (Plate 9, fig. 11) delimited by a 

 simple margin which denotes the inception of the pit cavity. 

 The shape of the latter is variable, depending upon the prox- 

 imity of other pits and the type of cells neighboring the 

 parenchyma. In ray parenchyma the simple pits may become 

 i to present a latticelike appearance. 



Poren in 



Phanerogamen, hauptsachlich der Leguminosen, Ber. Deutsch. 

 10 (1892) 494-513. 



