312 MESSES. CTEIL WEST AND H. TAKEDA ON 



3. Frimarij Cortex. 



The primary cortex of the youngest specimen examined by us is composed of large 

 parenchymatous cells packed with starch and proteid granules. In the younger part 

 of the plant these cells are isodiametric and form a compact homogeneous tissue, but 

 in the central region of the cortex the cells become loosely arranged with large 

 intercellular spaces. Towards the outer limits of the cortex these cells become 

 collenchymatous, their walls meanwhile increasing in thickness. At this stage the 

 starch-grains suddenly disappear, leaving a loose alveolar mass of protoplasm which 

 lias been * moulded,' so to speak, by the starch-grains before their disappearance. 

 PI. 38. liix. 60 shows a cortical cell in this condition; numerous proteid granules can 

 still be seen attached to the protoplasmatic framework. 



On the margin of the caudex no definite epidermis w^as observed, but the outermost 

 layers of cortical cells form a rudimentary periderm, the walls of these cells giving the 

 recognized suberin reactions on treatment with Sudan III., etc. 



A point of especial interest in connection wdth /. japonica is the presence of an 

 intracellular mycorrhiza in the peripheral cells of the primary cortex. The very fine 

 freely branched non-septate mycelium of the fungus was found in many of these cells. 

 No reproductive bodies of any description were noticed, but the hyphse formed numerous 

 spherical swellings [vesicules of Janse (i8, p. 143, PL 13. figs. 7, 8)], either terminally 

 or in an intercalary position (PI. 38. fig. 61). These swollen portions of the hyphse 

 contain, at an early stage in their development, a dense granular substance very similar 

 to that found in the hyphae themselves. The chemical nature of this granular 

 substance was not investigated ; it is probably a proteid substance. As these 'vesicules 

 increase in size they appear to lose their contents, the largest, and therefore, oldest 

 ' vesicules ' being quite empty. It is not known why these swellings are produced, but, 

 judging from their wide distribution in the mycorrhiza of several distantly separated 

 groups of plants *, they no doubt possess some unknown but nevertheless important 

 function connected with the nutrition of the fungus or of the host. 



Owing to the complete absence of reproductive bodies we were unable to determme 

 ViiQ systematic position of this endophytic fungus. 



Structtjre of the Secokdaut Tissues oe the Stem 



1. Canibium. 



In Isoetes japonica cambial activity starts very early; obvious periclinal divisions m 

 tlie outermost cells of the ' parenchymatous mantle * were observed in a very young 

 sporophyte, the greatest diameter of the caudex of which measured only 2 mm. Ihe 

 Civmbium, once formed, persists throughout the life of the plant ; more than one 

 cambium in the stem was never observed in our preparations. 



( 



