A VENA SATIVA. 1 95 



naked as in pine, but that it is surrounded by an organ 

 peculiar to angiosperms, the ovary, which in this plant 

 adheres to the surface of the ovule. It is much better 

 developed in Trillium and Capsella, to which for its 

 study the student is referred. Since the ovule is thus 

 inclosed, stigmas have been developed as naked pollen- 

 catching surfaces, to which the pollen spores can 

 adhere, and through whose loose tissues they can eas- 

 ily send their tubes. 



The adherence of the ovary wall to the ripened seed 

 gives rise to a fruit peculiar to grasses, the grain, which 

 is commonly mistaken for a simple seed. 



The fibre-vascular system is well developed in oats, 

 and is of the typical monocotyledonous form. The 

 hypodermal fibers of both stem and leaves give addi- 

 tional strength to these organs. The bundles through- 

 out the stem are of the collateral type, as in the pine, 

 but with this difference ; whereas in the pine there 

 remains a cambium layer between the xylem and 

 phloem, here there is no cambium. The continued 

 growth of the bundle is therefore impossible, whence 

 it is known as a closed bundle. The axial bundle of the 

 root is, like that of the fern, a radial one. In the fern 

 root a single apical cell forms the growing point of 

 the root ; in oats the apical cell is replaced by a clus- 

 ter of cells. The remark respecting the root-epidermis 

 of Adiantum " is equally applicable here concerning the 

 older roots. 



In the leaves the most novel structure is the groups 

 of hygroscopic, or as they were first named by Duval- 



24 Cf. also Goodale, Physiological Botany, p. 108. 



