478 SUMMAUY OF CUUnENT RESEARCHES lIELATIXa TO 



and branches. Hero also they appear to have a narrow, square, tabular 

 form, the nucleus being again spherical. Their reactions agree in 

 general with those of Pinguicula. 



In general terms the crystalloids in these plants agree, in their 

 character and qualities, with those of Lathrcea squanuxria ; all the 

 plants containing them being distinguished by a peculiar mode of 

 life. 



Tegumentary System of Roots in Phanerogams.* — L. Olivier 

 publishes a preliminary notice of the chief points arrived at in a study 

 of this structure in the roots of Monocotyledons, Gymnosperms, and 

 Dicotyledons. 



In Monocotyledons the peripheral layer of the root is usually, 

 with some exceptions, simple ; with the exception of the produc- 

 tion of rootlets, it docs not give rise to any tissue. There is no 

 true epidermal layer ; that which is usually so termed, and which is 

 commonly piliferous, is not continuous anatomically with the epidermis 

 of the stem, but is covered by a cap, one of the layers— and not 

 always the outermost — of which corresponds morphologically with 

 one of the sub-epidermal layers of the tigellum. In the great 

 majority of cases, tlie mode of formation of the stem is more or less 

 centripetal. 



In Gymnosperms —contrary to what occurs in Monocotyledons — 

 the primary cortex does not give rie-e to any tissue, and it is the rhizo- 

 genous layer that produces a secondary parenchyma towards the 

 interior, the bark towards the outside. 



Among Dicotyledons the secondary tegumentary structures vary 

 in their development acccjrding as the secondary vascular system is 

 formed early or late, as the plant is herbaceous or woody, and as the 

 root is aerial or terrestrial. A variety of cases are described differing 

 from one another in these points ; and the following are the more im- 

 portant results arrived at, where the secondary vascular system is 

 formed early. 



1. The peripheral layer of the central cylinder forms beneath it a 

 centrifugal secondary parenchyma. 



2. When the formation of this parenchyma becomes appreciably 

 unequal, as in the beau, the rhizogenous layer commences to divide 

 in order to give birth to the primary vascular bundles. 



3. This secondary parenchyma and the primary cortical paren- 

 chyma are always composed of large cells whose walls are coloured blue 

 by chlor-iodide of zinc, and are full of protoplasm ; they continue in an 

 active state during the whole life of the root when it is annual; a 

 large quantity of nutritive reserve-materials is stored up in them, 

 with which they are always gorged in winter. 



4. Normally the root has um suberous layer ; such is formed from 

 the bark only in a very irregular and accidental manner, and only in 

 those cases where the external primary cortical layers peel off. 



5. All the species of Dicotyledons observed were herbaceous ; in 

 woody plants the phenomena presented differ in many points. 



* Bun. Soc. Bot, Fiance, xxvii. (1880) pp. 233-41. 



