knowledge of the A natomy of Plants. 1 5 1 
wood in Tecoma as an adaptation of the climbing stem to 
tensile strains is a case in point. As a matter of fact, the 
internal wood is extremely porous and evidently in the main 
a conducting-tissue of little mechanical importance. As 
regards development, the mechanical tissue may arise from all 
regions of the meristem, and here there is consequently a 
sharp opposition between the developmental and physiological 
principles of classification. 
Secretory tissues. On this subject much work has been 
done. 
The widely -distributed secretory sacs appear to have 
become modified in certain orders in two directions, namely, 
into laticiferous vessels and laticiferous cells. The discovery 
that the latter are living elements with protoplasm and nuclei 
is due to Treub, Schmidt, etc. 
The function of laticiferous tissue is supposed by Haber- 
landt to consist in the conduction of assimilated food. The 
observations of Schimper, Groom, Boodle, etc. show, however, 
that the relation of these tubes to the assimilating system is 
not a constant one. 
The very early development in embryonic tissues is com- 
mon to laticiferous tubes and certain secretory sacs. 
As regards intercellular secretory spaces these differ from 
the sacs in the fact that the secretion leaves the cell in which 
it is formed. The distinction between lysigenetic and schizo- 
genetic spaces depends on the fact that in the former the 
cells become completely used up in the process of secretion, 
while in the latter the same cells remain living and may 
continue their functions indefinitely. 
The schizogenetic mode of origin appears to be much more 
usual than has been supposed, and very probably all secretory 
spaces begin in this way, e. g. Rutaceae and Myrtaceae. In 
the glands of Myoporum the cells fuse, their nuclei remaining 
for a time distinct. 
Vascular bundles. As regards the main points in the dis- 
tribution of bundles there is little to add to the elaborate 
account of de Bary. The curious parallelism discovered by 
