PRIMULA CONFERENCE. 



237 



tion, of transformation, which, with or without the agency of minute Bacterian 

 organisms, constitute each root-tip, each root-hair, a laboratory and a work- 

 shop. Each root-tip, each root-hair, moreover, is as sensitive as a nerve, not 

 only responding to a touch, but transmitting impressions from the spot touched 

 to adjoining cells. It is as mobile as a muscle, turning towards what is useful 

 to it, bending away from what is noxious or obstructive, threading its way 

 through the soil, and adapting itself to circumstances as if it really possessed 

 intelligence. It acts like the brain, says Darwin ; and truly as a sentient 

 organ, receiving and transmitting impressions and directing the course of 

 growth and movement, it would be hard to say wherein its inferiority to the 

 nervous system of the lower animals consists.* 



In the case of annual plants, which live their life within the compass of a 

 few weeks or months, there is little else for the root to do than to secure the 

 plant in the ground and to go in search of food and turn it to account when 

 found. 



But in the case of perennial plants, such as most of our Primulaceae, another 

 duty becomes incumbent— that of providing a store-place for water and for 

 food. The food so stored, principally starch and allied substances, is not 

 absorbed directly by the root and packed away, but, partly by root-action and 

 soil-food, partly by leaf-action and air-food, is manufactured in the leaves and 

 afterwards transferred and deposited in the root or in the root-stock. 



A similar formation of starch takes place in annual plants, but the starch is 

 used up in the process of growth, or stored in the seed to be turned to use by 

 the seedling plant when it begins life on its own account. In any case the 

 storage requirements of an annual are small in comparison with those of a 

 perennial. To ascertain how and in what manner the food is obtained, 

 transformed, stored, and employed, is surely to put ourselves in possession of 

 information, of any that could be named, the most important for cultural 

 purposes. 



Another phase of work which it falls to the lot of the root (sensu latiori) 

 to achieve is that of propagation, and by observing how this is effected spon- 

 taneously we may surely obtain some useful hints for our own artificial 

 procedures. 



Such, then, in very general terms, is the nature of the work to be done ; 

 such, in merest outline, are the requirements of the case. 



The Mechanism. 



In the following remarks it is proposed to give a few illustrations , 

 of the machinery by means of which the work just alluded to is done, for 

 while the work is in all cases the same, the machinery by which that work is 

 accomplished is manifold in detail. 



* Since this paper was written, further additions to the marvels of root-action have 

 been made known by MM. Van Tieghem and Douliot (see Bulletin Soc. Botan. 

 France, 1886, p. 252). Roots, as is well-known to botanists usually originate in the 

 deeper tissues of the plant, and hitherto they have been considered to force their way 

 outward by mechanioal pressure during growth. The two Botanists above-mentioned, 

 have, however, ascertained that the growing root-cells secrete some fluid which enables 

 them to soften, ultimately dissolve, feed on and digest the cells with which they come 

 in contact, much in the same way that the same roots, when they have accomplished 

 their escape from the inner substance of the plant, fed on the particles of soil with 

 which they come in contact. Messrs. Van Tieghem'sand Douliot' s observations were 

 largely made in Primroses of various kinds. 



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