LINAIUA CYMBALARIA. 201 



invariably of the purple colour which characterise so many of the 

 leaves of the fuU-grovn plant. 



Passing on to the characters of leaves, roots, and plant-stems, 

 I will shortly call attention to their several structures. 



The Leaves of the fully-grown plant are quinquangular in 

 shape, seated on very long foot-stalks. The upper surface is of a 

 dark, shining, green colour ; the under surface of a metallic grey. 

 I have already remarked upon the purple tint of the under surface 

 of many of the leaves. The cause of this peculiarity was sought 

 for unsuccessfully by a correspondent to Science Gossip four or five 

 years ago. He suggested that probably some change takes place 

 in the chlorophyll of the cells. This is hardly satisfactory, as the 

 purple tint is not, as it is in so many plants, the sign of approach- 

 ing decay. The beautiful colour is very abundant in the leaves of 

 the seedlings, so that the tint is due to colouring matter similar to 

 that which imparts beauty to the petals of our garden and green- 

 house flowers. The variety in colour of these leaves adds ele- 

 gance -to the tiny Linaria. The blossom is small and not deeply 

 tinted ; consequently, it would not attract very great attention. 

 But when from among the bright green leaves many of them curl 

 and exhibit their purple and almost crimson under surfaces, the 

 attractive qualities of this little plant are considerably enhanced. 



The Cuticle of the leaves is well worthy of consideration. 

 The upper cuticle is detached with very great difficulty, and I have 

 not. been able to obtain good specimens, although the leaves have 

 been boiled in diluted acid. It contains no stomata, and the cells 

 are of an ordinary shape. The under cuticle is one of the most 

 beautiful of its kind. It is a tough membrane, readily detached, 

 with large cells of sinuose character ; they appear to contain but a 

 small quantity of chlorophyll. This cuticle becomes too transpa- 

 rent for observation when mounted in balsam, and therefore must 

 be stained before mounting. 



The Stomata are confined to the under cuticle, and they vary 

 in point of numbers in different plants and in different portions of 

 the same leaf. I have paid a little attention to their frequency, 

 and from one specimen I calculated that a square inch of surface 

 would contain about 1079 stomata. They are exceedingly minute, 

 and possess the usual kidney-cells around the fissures of the 



