52 BIOLOGY. [Book i. 



substances tending to become crystalloidal and to be expelled 

 from tlie organism. The vitality of the blastemas is naturally,, 

 greater than that of the plasmas ; they may almost be considered 

 as elements which have lost their foi-ms ; physically, they are 

 viscous liquids in which, generally, granulations are interspersed. 

 They are the organisable liquids by excellence. It is in the 

 midst of the blastematic liquids that the anatomical elements 

 of the embryons, or of the tissues constituted in process of 

 development or regeneration, have their origin,, for instance, 

 after a wound. 



1. — Vegetal Blastemas. 



The plants, even the most perfect, the dicotyledons, have no 

 special circulatory system. In the dicotyledonous tree, the terres- 

 trial sap mounts through the tissues of the wood, filling the 

 interoellulary spaces, the canals, and passing by endosmosis 

 from cell to cell, from fibre to fibre. Arriving at the leaves it 

 undergoes an important modification, with which we shall have 

 to occupy ourselves ; then it redescends by the more superficial 

 tissues, and especially by the young intermediary tissues between 

 the bark and the wood. The descending sap, that which has 

 been elaborated in the leaves, must be considered as a living 

 liquid, as a blastema ; also, as it goes along we see it organising 

 itself either in a direct mannei- or through the agency of pre- 

 existent anatomical elements. In truth it is a liquid holding a 

 middle position between the plasmas and the blastemas. 



The blastematic liquidj whence spring the buds, is thoroughly 

 comparable with the animal blastemas. Like these last it is 

 in part exuded by the anatomical elements, that is to say by the 

 vegetal cells which it drains ofi and dissevers. This mode of 

 formation recalls that of the vegetal and animal embryonary 

 blastemas. 



The true vegetal blastemas resemble much the semi-liquid 

 azotised content of the vegetal cells, namely, that intracellular 

 substance endowed with spontaneous movements, having its 



