266 SUMMARY OF CURRENT RESEARCHES RELATING TO 



forms occur in both cases, cither resembling the other form or small 

 nnd rounilish. The bean-form occurs in Faba and DoUchos, viz. small 

 oval grains with longitudinal fissure. 



Function of Latex in the Compositse.* — Mile. A. Leblois has 

 confirmed, by a special scries of experiments, the view of Van Tieghem 

 that the latex is of the nature of a secretion, rather than that of 

 IM. Faivre, that it is a reserve food-material. A strong confirmation 

 of this view is that the latex, as for example in Scorzonera, is entirely 

 wanting in the embryo. 



Influence of Light on the Development of the Assimilating 

 Tissue of Leaves.f — S. Grosglik has examined the structure of the 

 heteromorphic leaves of Eucalyptus globulus, and finds that the differ- 

 ence in form corresponds to a difference in anatomical structure. 

 The assimilating tissue of the horizontal leaves is constructed on the 

 dorsiveutral type, while in the narrow vertical leaves the two sides 

 are precisely alike. The latter show palisade-parenchyma on both 

 sides, the former on the upper side only, the lower side being pro- 

 vided with spongy parenchyma. The young leaves have always at 

 first a vertical position, from which they pass gradually to the 

 horizontal, their internal structure going through corresponding 

 changes. In the vertical leaves the tissue immediately beneath the 

 large-celled epidermis is composed of similar isodiametric cells, 

 having in its centre a yet feebly developed vascular bundle. It 

 already contains chlorophyll-grains. Grosglik proposes for this 

 tissue the term primary mesophyll. From this primary mesophyll 

 the assimilating palisade-parenchyma is developed at a subsequent 

 stage. It is formed at first beneath the epidermis on both sides of the 

 leaf, and is even more strongly developed on the under side ; at one 

 period the mesophyll consists almost entirely of palisade-parenchyma ; 

 but as the under side of the leaf passes more and more into the shaded 

 condition, it gradually becomes converted on that side into spongy 

 parenchyma. 



In other leaves examined by him the author finds that the forma- 

 tion of true palisade-parenchyma is preceded by that of primary 

 mesophyll, which has been mistaken by Pick t and others for palisade- 

 parenchyma ; the differentiation of palisade and spongy parenchyma 

 takes place only at a comparatively late stage. 



Cortical Fibrovascular Bundles of Viciese.§ — In the tribe Viciero 

 of PapilionacefB the stem is furnished with cortical fibrovascular 

 bundles ; and the leaves being distichous, the number of these bundles 

 is reduced to two. In most cases, at each node the cortical bundles 

 completely disappear and are completely replaced ; but P. Van 

 Tieghem describes several departures from this normal structure in 

 various species and in the same species at different periods. 



* Bull. Soc. Bot. France, xxxl. (1884) pp. 122-i. 



t Bot. Centralbl., xx. (1884) pp. 374-8. 



X Sec this Journal, iil. (188:)) p. 92. 



§ Bull. Soc. Bot. Fiance, xxxi. (1884) pp. 133-5. 



