580 Goodlattk: The anatomy of Parosela spinosa 



brown in color (figure 6). Weyland speaks of finding only traces 

 of this epithelium at an early stage in the formation of the gland, 

 and says that it later breaks down and a schizogenous-lysigenous 

 gland results. In the species P, spinosa this is not the case, as the 

 epithelium is plainly marked even in a gland occurring on an old 

 spine, where it is presumable that the gland is of a considerable 

 age. It is glands of this type which form the lumps on the young 

 branches, alluded to by Solereder, and which occur at the bases of 

 the stipules. They occur in numbers In the palisade tissue of the 

 primary cortex, but are naturally absent from the older branches 

 on which the periderm has supplanted the cortical tissue. 



In the attempt to decide on the nature of the contents secreted 

 by these glands, we have again to record no result In this case 

 it would seem that the contents have been extracted. Weyland 

 finds round glands of the same type In all the genera of the sub- 

 tribe Psoraleae that he examined. They contained a light or dark 

 yellow resin, which was soluble in alcohol. The occurrence of 

 these glands with resinous contents is a character for divisions 

 greater than a genus, he claims. Therefore, since glands of the 

 same structure and' position contain resin in other species of 

 the genus and subtribe, and since the resin is soluble in alcohol, 

 it seems safe to conclude that the contents were resinous and have 

 been extracted by the alcohol in which the material was placed. 



This completes the secretory apparatus of the stem. The 

 leaves contain the same round glands, which appear in either the 

 palisade or spongy tissue, opening toward either surface. No 

 trace of tannin ducts nor of the single isodiametric tannin-secret- 

 ing cells, nor of the layer of tannin cells in the mesophyl, men- 

 tioned by Baccarini as present in the group, could be found. In 

 addition to the resin-bearing glands, however, the leaves contain 

 a peculiar type of gland, the so-called intercellular glands. These 

 are composed of elongated cells which have split apart from each 

 other, so that in the mature gland they present the appearance of 



strands of tissue running through the cavity of the gland. A 



the whole is a sheath of close-set cells, developed from the 

 mesophyl (figure 7). It is only in the mesophyl tissue and 

 opening on the under side of the leaf that glands of this type 

 occur. Their contents are small pieces of hardened brown stuff. 



