300 Miscellaneous. 



Below, these fibres terminate in a point, without attaching'thern selves 

 to any analogous organ ; above they are continuous with a fibrous 

 sheath surrounding the stylar canal ; laterally they are in contact 

 with the annular parenchyma which surrounds the placenta, and 

 becomes converted into suberous tissue at maturity, causing the 

 dehiscence of the fruit and the separation of the valves. In the 

 genus Cardamine, of which the dehiscence is different, the herbaceous 

 layer of the placenta is interrupted at the level of the line of attach- 

 ment of the valves. 



In certain Cruciferse, which have a free funiculus and a spherical 

 indehiscent fruit, these fibres do not exist, and the horizontal section 

 of the fruit only shows tracheae ramifying in a parenchyma. 



The anatomical structure of the septum has not yet been thoroughly 

 investigated. Its two lamellae present at first cells filled with green 

 matter, which in some rare cases is retained until the fruit is mature. 

 The form gradually acquired by these cells, the direction of their 

 elongation, and the thickness of the membranes formed by them 

 may furnish specific and even generic characters for the Cruciferse. 

 The Alyssinece may even be divided into two sections according to 

 the form of the septal network. 



Fibres and vessels are frequently developed between the two 

 lamellae. Sometimes the cells of the septum acquire the character 

 of fibres upon the median line. In many cases there exists in the 

 middle of the septum a fibrous bundle, which encloses a dotted duct 

 in Sisymbrium tanacetifolium. In Matthiola, Malcolmia, and several 

 Sisymbria, of which the author makes a distinct group under the 

 name of Malcohniastrum, there is between the two lamellae an actual 

 membrane formed of juxtaposed fibres, among which are some 

 tracheae. 



In some genera, especially Farsetia (excl. Fibigia, Dec), the fibres 

 of the septum are pierced with holes, by which they communicate, 

 forming a very elegant network unconnected with any fibro-vascular 

 bundle. 



In Psychine stylosa the septum, which is very transparent and 

 formed of polyhedric cells with delicate and inconspicuous walls, pre- 

 sents long branched tubes of very unequal diameter, with distinct 

 walls and greenish granular contents before the maturity of the fruit. 

 These tubes generally ascend nearly parallel to each other ; but they 

 anastomose irregularly, so as to resemble a laticiferous network. 



But it is in the triangular canal that these formations, sometimes 

 closely resembling certain varieties of laticiferous vessels, are especially 

 met with, containing, however, only granules of chlorophyll, starch, 

 and fatty matters. They consist of isolated ramose cells, or more 

 frequently of elongated lateral vessels emitting branches at right 

 angles to their direction. Among the various elements of this system 

 we may observe sometimes complete partitions communicating by 

 the ordinary punctures, sometimes walls perforated like sieves, some- 

 times open canals, probably produced by the disappearance of former 

 partitions. 



These anatomical observations throw a new light on the constitu- 



