SOME FEATURES IN THE ANATOMY OF THE MAL VALES 
possessed the diffuse type, and therefore, in this respect, represent a 
high development among the Malvales. 
The Javanese species chosen from the Bombaceae, Durio zihe- 
thinus L., presents very interesting characters. Figure 13 shows a 
transverse section of a mature branch. Abundant diffuse parenchyma 
cells, including crystals, are characteristic for the species in addition 
to the normal type as found in the Tiliaceae. Figure 14, a higher mag- 
nification of the same area, shows better the average distribution of 
parenchyma, the cells of which are distinguished from the fibers by 
thin walls, simple pits, and crystals. Returning to figure 13, the central 
portion shows a departure from the normal structure in the presence 
of an aggregate ray with its included fibers. Figure 15, a radial 
section from the same material, shows, besides the rectangular paren- 
chyma cells, those which have undergone secondary division to cubical 
cavities in which crystals are deposited. The aggregate structure 
of the ray shows even more clearly in a tangential section, figure 16, 
and in figure 17, a higher magnification of a single ray with its included 
fibers, which are in the process of transition to parenchyma, as is 
indicated by the septate condition. Figure 18 is similar to figure 16 
except that a leaf-trace is included, thus showing the origin of the 
aggregate ray. The reason for the gradual transition to the diffuse 
type can be seen by a careful study of the tangential sections which 
show that all the included fibers are septate, an indication of transition 
to normal ray parenchyma without included fibrous elements. 
The presence of aggregate rays in an order in which the diffuse 
type is normal is significant. Reference has already been made to 
the relative development of rays in which it w^as stated that the 
aggregate rays indicate a more primitive condition than those of a 
diffuse character, which points to the conclusion that, since Durio 
possesses this type of ray, it represents a more primitive condition 
than any of the other species of the Malvales described in this paper. 
Still further proof of the presence of aggregate rays was presented 
by serial sections through several annual rings of growth in a stem 
which showed no indication of having been wounded, which, with the 
abundance of diffuse parenchyma, may be considered as indicative of 
primitive conditions. Consequently, so far as the anatomy of the 
stem is concerned, it is evident that Durio is the most primitive of the 
Malvales examined, since it still retains the aggregate ray as well as 
abundant diffuse parenchyma, which conditions are very similar to 
