LINEAR AND CLUSTERED ARRANGEMENT. 795 



clearly lineal arrangement from the mycelial threads running below the surface of 

 the ground and in dead, rotten tree-trunks. Some Mosses form colonies in very 

 regular lines from their rhizoids and horizontal underground protonemas. The most 

 conspicuous, however, is the line formation produced by roots which run horizontally 

 below the soil. The Aspen (Populus tremula), the Sea Buckthorn (Hippophae 

 rhamnoides), Lycium barbarum, the Raspberry (Rubus Idceus), the Dwarf Elder 

 (Sambucus Ebulus), Asclepias Comuti, various species of Linaria and Euphorbia, 

 and numerous other plants (cf. p. 27) produce special horizontal underground roots, 

 which give off buds towards the upper side. The shoots arising from these buds 

 form separate independent plants after the root which formed them has died away. 

 Obviously the plants follow the direction of the roots, and are arranged in rows. 

 Even for years afterwards the line-like arrangement of the individuals in such 

 colonies can still be recognized. When the bud-forming roots are of considerable 

 length, the terminal offshoots are sometimes situated at some distance from the 

 mother-plant. I saw single offshoots from the root of an Aspen push up through 

 the ground 30 paces from the woody parent stem. Stems of Asclepias Comuti 

 spring up from the thick horizontal roots deep under the ground, at intervals of 

 about 40 cm., and in them also can the linear arrangement be sometimes very 

 clearly seen. When the individual offshoots in their turn give rise to horizontal 

 roots, the line-formation is lost sight of more and more, and a scattered group 

 spread over a wide area is the result. Sometimes the older portions of the colony 

 die off completely, and as the individuals in one direction disappear, those in the 

 other grow more luxuriantly. One might almost suppose the whole group to have 

 taken a few steps forwards. This phenomenon can be seen particularly well in 

 Raspberry bushes. On suitable soil a group of Raspberries will move about 2 paces 

 every year, and therefore, after 10 years, they may have moved about 20 paces. If 

 Raspberry bushes are planted near an inclosed piece of ground along a fence or 

 hedge, it may happen that ten years later not a single one can be seen in the original 

 place, while on the other side of the fence, in the neighbouring piece of ground, quite 

 an assemblage of Raspberry plants has come into existence. 



The clustered or linear colonies which spring from underground tubers have the 

 following very simple history. After a tuber has been fully formed on the under- 

 ground shoot of a plant the slender bridge-like connections which have hitherto 

 served for the conduction of food break down by the decay and decomposition of 

 their tissues. The new tubers thus separated from the mother-plant send out stems 

 from their buds, after the necessary period of rest these push up above the ground 

 and also give rise to new subterranean shoots with tuberous swellings. These 

 fresh tubers, after they have become disconnected, again form the starting-points for 

 tuber-forming plants. This goes on until after a few years the soil all round the 

 place where the first tuber had been is crowded with hundreds of separate tubers, 

 and corresponding to these above the ground is a group of hundreds of separate 

 leafy stalks. It depends of course on the number and length of the underground 

 tuber-forming shoots whether the group is crowded or scattered. In the Artichoke 



