PLANT TISSUES 149 
meristem but sometimes the dermatogen gives rise to them, as 
in Clove, Myrtle, Asarum, etc., or both the ground meristem 
and dermatogen may contribute to the formation of the same 
gland. Internal glands and secretion reservoirs are termed 
schizogenous when the secreting cells split apart at the center of 
the group and draw away from the line of separation, as in the 
Fic. 87.—Schizogenous secretion reservoir (resin duct) as seen in cross section 
in the young stem of English Ivy. A, early and £, later stage in the formation of 
the duct. g, the mature duct; c, cambium; wh, phloem; 4, bast fibers, rp, 
parenchyma. (Stevens, after Sachs.) 
stems and leaves of the pines; when they break down completely, 
leaving their secretion in the resulting cavity they are termed 
lysigenous, as in the rinds of the orange, lemon and other Citrus 
fruits. The secretion reservoirs, also called internal tubular glands, 
are formed by a long vertical series of cells forming a space 
schizogenously or lysigenously. The schizogenous type of 
gland and reservoir is lined with a layer of cells, usually more or 
less flattened, which are characterized by possessing large nuclei. 
To this layer has been assigned the name “secretory epithelium.” 
