ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 59 



BOTANY. 



GENERAL, 



Including the Anatomy and Physiology of Seed Plants. 



Structure and Development. 

 Veg-etative. 



Clusiacese of North-west Madagascar ; the Influence of the Soil 

 upon their Secretory Apparatus.* — H. Jacob de Cordeuroy publishes a 

 detailed account of his investigation of this subject, and arrives at some 

 very definite and interesting results. The number and dimensions of 

 the secretory organs, he finds, are variable, and the variations are the 

 direct result of the character of the soil. These organs are, generally 

 speaking, extensively developed in plants growing on primitive rock 

 soils (gneiss, basalt, crystalline schists), and relatively poorly developed, 

 for the same species, where the soil is the product of sedimentary rocks, 

 especially sandy and calcareous soils. This distinction is strikingly 

 illustrated in the case of Ochrocarpus angustifolius. 



The secretory apparatus consists of canals, in the following regions : 

 cortex, pith, primary bast, and secondary bast. Two main types emerge, 

 according as the apparatus is the more conspicuous in the primary tissue- 

 systems (Garcima verrucosa, Tsimatimia Pervillei), or in the secondary 

 tissue, the secretory system in the primary tissues being relatively re- 

 duced {Tsimatimia pedicellata, Symphonia sp.). In Ochrocarpus the 

 secretory organs are evenly distributed among primary and secondary 

 tissues. The canals in the cortex seem to be present invariably, 

 whether the soil be of igneous or sedimentary origin ; the pith canals, 

 on the other hand, often disappear in the latter case (Rheedia, Sym- 

 phonia, 'Tsimatimia) ; while secretory canals tend to be suppressed 

 from the primary phloem of Ochrocarpus when grown on sedimentary 

 soils — a significant fact when it is remembered that their presence in 

 this tissue is a recognized anatomical character of this genus. Dry- 

 ness of the soil, moreover, has its effect upon the secretory system. 

 The medullary system is reduced, or disappears as a consequence ; and 

 when the soil is sedimentary, secretory organs do not tend to appear in 

 the bast, by way of compensation, as they do in the case of igneous 

 soils {Tsimatimia pedicellata, Symphonia). Altitude, again, seems to 

 induce diminution in the activity of resinous secretion (Symphonia 

 clusioides, Ochrocarpus eugenioides). 



The author draws the obvious and important conclusion that, in 

 view of this variability, extreme caution must be used in the employ- 

 ment of the extent and disposition of the secretory system for the 

 purposes of classification in this group. 



* Ann. Sci. Nat. Bot. xi. (1910), pp. 287-359. 



