300 The Philippine Journal of Science 1923 



the ray cells are somewhat larger (36 to 126 /* in length and 

 10 to 54 ft, in height) and generally contain infiltration products 

 in larger amount than do the vertical cells. As in the other 

 features, the rule for cell dimensions applies; namely, cell 

 height varies inversely to cell length. 



Crystallogenous idioblasts.— (Plate 2, fig. 2, and Plate 7.) 

 Crystallogenous idioblasts are abundant in the macerated wood of 

 Parashorea malaanonan (Blanco) Merr., either as isolated cells 

 or in short rows, and they may arise from either the vertical or 

 the ray parenchyma, though more commonly the former. When 

 arising from the vertical parenchyma, the cells of a vertical row 

 become further segmented by the septa into a beadlike or catenate 

 string of compartments, twenty-five or more in number, in each of 

 which a solitary tetragonal crystal of calcium oxalate is formed. 

 The new cross walls thus formed are typically parenchymatous 

 in nature, both in pitting and in thickness, and the identity of 

 the original parenchyma cells is completely lost. Such idioblasts 

 are to be regarded as depository organs, and the calcium oxalate 

 is undoubtedly a waste product in plant metabolism. 15 



The idioblasts that arise from the ray parenchyma are not 

 so abundant nor so conspicuous in macerated material as are 

 those of the vertical type. As in the case of the longitudinal 

 rows they are formed through subsequent septation of ray cells 

 into from two to five compartments, in each of which a tetragonal 

 crystal forms. The crystals are smaller as a rule than those 

 contained in the vertical idioblasts. 



The preceding paragraphs have been devoted to a study of the 

 individual elements of Parashorea wood as they appear in macer- 

 ated material, and indicate the wide departures in cell types 

 that are correlated with varying function. The disposition of 

 the different elements in the cell aggregate that we know as 

 wood may now be studied to advantage at higher magnifications 

 and the significance of the grouping more readily understood. 

 In the following pages the wood of Parashorea malaanonan is 

 discussed in detail as it appears in the three planes of section. 



Cross section. — (Plates 3, 4, and 22.) In cross section at mag- 

 nifications of 50 to 100 diameters, the vessels stand out very 

 conspicuously, owing to their abundance and their large size, and 

 appear as rounded pores that are sharply delimited at the margin 



