THE LOCALISATION OF ENZYMES IN PLANTS. 353 



in the pericycle and the bast of the veins. In a few- 

 cases they occur in the endodermis of the bundles. 

 In the Capparidacese they are found two or three 

 together, the groups extending throughout the par- 

 enchyma. 



Flowers. — In Capparidacese the flower contains large 

 numbersof the secreting cells in both sepals and petals. 

 They are most numerous in the pulp of the fruit. 

 In this order they are arranged in the flower and 

 fruit into little groups, each of which is developed 

 from a single cell which becomes prominent while the 

 tissue is still very young. In Tropaeolum they are 

 very prominent in the tissue of the spur. In the 

 flowers of Cruciferae they are chiefly met with in the 

 carpels, particularly in the neighbourhood of the 

 hbrovascular bundles. 



Seeds. — In Cruciferae the integuments of the seed alone, 

 or both embryo and integument may contain them. 

 Guignard distinguishes five types of localisation : — 



(1) The cotyledonary parenchyma and the cortex 



of the axis of the embryo. 



(2) The tissue abutting on the back of the cotyle- 



donary bundles, or the pericycle if that layer 

 is differentiated ; also in the cortex of the 

 axis. 



(3) Both regions described under (1) and (2). 



(4) Sometimes they are absent from the radicle 



and the cotyledons. 



(5) The integument only. 



In the Limnantheae these cells can be detected in the 

 parenchyma of the cotyledons when the seed is very 

 young, and before any reserve materials are stored 

 in any of the cells. Later, on germination, they can 

 be recognised in the lower epidermis when the cotyle- 

 dons become green. The other orders show a 

 similar distribution. 



Guignard also ascertained the distribution of emulsin, 



the ferment of the almond and laurel. In the leaves and 



young branches of the latter plant the endodermis of the 



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