322 THE BEGINNINGS OF LIFE. 



their mode of origin even more certain than it had 

 been before. In some situations they were something 

 like tadpoles in shape, whilst in others they were 

 cylindrical, or only very slightly attenuated towards 

 one extremity. But M. Trecul tells us and no one 

 is more competent to pass an opinion on such a 

 subject that c the appearance of these little plants 

 within closed cells, occupying their natural situa- 

 tion in the very middle of the medullary tissue, 

 negatives all ideas as to the introduction of germs 

 from without. 5 And he has even seen similar organ- 

 isms produced within fibre-cells of the bark which had 

 already become notably thickened, in Ascleplas cornuti 

 and also in Met ap lexis chmensis. (See Fig. 71, a, e.) 



But M. Trecul is able to add another proof even more 

 striking than any we have hitherto mentioned. He has 

 actually seen a crystalline mass undergo modifications, 

 and become itself converted into an Amylobacter. There 

 exists, he says, in the bark of the common Elder, 

 and in that of plants belonging to different families, 

 such as Solanace<e and Crassulacea^ a number of cells 

 which are filled with little tetrahedrons having slightly 

 unequal sides. These cells may be isolated, or they 

 may be grouped in contact with one another, and in 

 longitudinal series. The cell-walls sometimes become 

 partly absorbed, so as to form intercommunicating 

 lacunae, and it is within these that the enclosed 

 tetrahedrons become converted into starch-bearing or- 

 ganisms. M. Trecul says: c Since my observations 



