326 
SUMMARY OF CURRENT RESEARCHES RELATINO TO 
undergo a comparatively large development. The absorbing organs are 
formed in different ways, and exhibit a great variety of form. These 
organs lie in the superficial layers of the substratum, and are always 
connected with the presence of mycorhizal hyplias, the function of which 
is obscure. These hyphae appear to enter the plant only by cells which 
are specifically absorbing cells. In the cortical cells which are attacked 
by these hyphae, the nuclei grow, and become much more deeply staining, 
indicating possibly a beneficial effect on the host. The absorbing organs 
are generally characterised by the large size of the cortex and the small- 
ness of the central cylinder. In the case of holosaprophytes (those 
entirely destitute of chlorophyll) the leaves are reduced to mere scales. 
Heterotrophy and Anisophylly. — Prof. J. Wiesner* * * § proposes the 
general term Trophy for all unilateral excesses of growth in tissues or in 
organs which are dependent on the position of the organ in question, the 
term position being understood in a wide sense, as the relation in space 
of the heterotrophic organ to the horizon and to its parent-shoot. 
Heterotrophy may be exhibited in epitrophy or hypotrophy of the 
axillary buds ; in epitrophy of adventitious buds ; in epitrophy or hypo- 
trophy of the shoot ; and in exotrophy or endotrophy. In relation to 
the cause of the unequal supply of nutriment which results in unequal 
growth, we may have phototrophy , geotrophy , or hydrotrophy. Anisophylly 
may be the result of a combination of all these last three forms of trophy, 
and has for its object to place the organ in a convenient position for 
illumination without any twisting of the internodes. 
From observations on anisophylly in Acer platanoides , Herr A. 
Weisse j* concludes that it is dependent on the position of the shoot in 
relation to the horizon, and also in relation to its parent-shoot. The 
greater length of the stalk of the lower leaves is the result of a weaker 
illumination. 
Dependence of the Form of the Leaf on the Intensity of the 
Light .J — From experiments on cultivating the harebell, Campanula 
rotundifolia , under various conditions as to exposure to light, Prof. K. 
Goebel concludes that its heterophylly may be traced to the effects of 
light. The lower rounded leaves, with a sharply defined petiole, are 
formed in a weak, the upper lanceolate leaves, with no well-defined 
petiole, in a stronger light. The formation of the basal cordate leaves 
has, however, become hereditary, and independent of external conditions. 
Other examples are given of the direct influence of moisture and light in 
determining the form of organs. 
Stem and Leaf of Euphorbiacese.§ — Herr W. Froembling describes 
in great detail the structure of the leaf and stem in a large number of 
genera and species belonging to the two tribes of Euphorbiaceae, Croto- 
neae and Euphyllantheae. 
* Ber. Deutsch. Bot. Gesell., xiii. (1895) pp. 481-95. Cf. this Journal, ante, 
p. 204. f Tom. cit., pp. 376-89 ; xiv. (1896) pp. 96-100. 
t SB. K. Bay. Akad. Wiss. Miinchen, xxv. (1896) pp. 331-5; Flora, lxxxii. 
(1896) pp. 1-13 (4 figs.). Cf. this Journal, 1895, p. 334. 
§ Bot. Centralbl., lxv. (1896) pp. 129-39, 177-92, 241-9, 289-97, 321-9, 369-78, 
403-11, 433-42 (2 pis.). 
