188 PITH IN EOOTS. [BOOK i. 



said, that owing to the elevation of the seed leaves in the 

 above cases, the place of the collum must have been rendered 

 doubtful, and that of the commencement of the real root 

 uncertain, then I will present a case from which doubt is 

 altogether excluded. 



"On the 15th of July, 1836, I stumbled on a seedling of 

 Corylus Avellana. I took it up with much care and found 

 that the seed lobes and half of the investing shell were still 

 attached to it. The stem measured seven inches in length, 

 with three or four leaves. The root measured three or four 

 inches in length, with many lateral fibres ; and the diameter 

 of the plant, at the widest, was about one-eighth of an inch. 

 In taking a longitudinal section of a portion of the root and 

 stem so as to pass through the collum, which could not 

 be mistaken, as the lobes never rise above the level of the 

 soil, it was evident that the pith, strictly cellular and under 

 the aspect of a fine thread, descended into the root, without 

 any node or interruption, or breach of continuity whatever, 

 and without any appreciable difference beyond that of colour. 

 Above the collum it was of a deep red; below it was of a 

 pale green. If any doubt remains in the mind of the reader 

 as to the accuracy of this statement, I shall be very glad if he 

 will have the goodness to repeat the experiment on a seedling 

 of the same species and of the same age, and to say what he 

 thinks of it then. With regard to myself, I hold it to be 

 a most satisfactory proof of the existence of a pith in the 

 descending axis even of Exogens. It may be seen equally 

 well in the root of seedlings of the Oak and Ash, but without 

 the peculiarity of the red and green colours." 



The pith is always, when first forming, a uniform compact 

 mass, connected without interruption in any part ; but the 

 vascular system sometimes developing more rapidly than 

 itself, it occasionally happens that it is either torn or divided 

 into irregular cavities, as in the Horse Chestnut, the Rice- 

 paper plant, and many others ; or that it is so much lacerated 

 as to lose all resemblance to its original state, and to remain 

 in the shape of ragged fragments adhering to the inside of 

 the vascular system : this is what happens in Umbelliferous 

 and other fistular-stemmed plants. 



