PROCUMBENT AND FLOATING STEMS. 661 



those which climb (stirpes scandentes), and the erect columnar stems (stirpes 

 palares). 



PROCUMBENT AND FLOATING STEMS. 



If we review the plants whose characteristic appearance is chiefly due to their 

 procumbent foliage -stem, we notice that most of them take root in turf, boggy 

 ground, on the stony plateaus of hilly districts, in the rocky clefts of wind-swept 

 mountain heights, or, lastly, in the sandy plains of the lowlands; in general they 

 inhabit an infertile soil, on which the storm has free play, and where erect plants 

 would find it difficult to maintain themselves. The leaves of such stems are usually 

 undivided and small, and are present in large numbers on each year's growth. 

 Where their number is small, and where correspondingly the internodes of the 

 annual shoot are more elongated, the leaves are often divided, but then the indi- 

 vidual segments are of the shape exhibited by the leaves of the short-membered 

 shoots. The leaves always appear in two or three rows on the fully-formed pro- 

 cumbent stem, whether they are decussate or spirally arranged (cf. p. 417). Where 

 no local insurmountable obstacles exist, the procumbent stems spread out in all 

 directions from the spot where the plant first took root, and when the species in 

 question are sociable weave a close carpet over the ground in a relatively short time. 

 In the earliest stages of development the shoots are not extended over the ground, 

 that is to say, the primary shoots, originating directly above the hypocotyl, are at 

 first erect. Soon, however, as it elongates, the stem inclines to one side and nestles 

 to the ground, or it arches over so that its free end reaches the soil. The apex of 

 course is always more or less erect, and most young, procumbent shoots have the 

 shape of an CO . As the stem elongates, the part immediately behind the growing- 

 point always nestles to the ground. In many instances these stems have not the 

 strength to hold themselves erect; the soil on which they lie is their actual bed or 

 support. If stems like these are held up above the ground, they hang limply down, 

 as may be seen in the Periwinkle (Vinca), Strawberry (Fragaria), and in the 

 Japanese Saxifrage (Saxifraga sarmentosa) so often grown in hanging baskets. But 

 in all cases it is not their weight merely which causes many shoots to assume this 

 manner of growth, in other words, that the shoots do not sink to the ground 

 under the burden of their leaves, can be seen plainly enough in the procumbent 

 stems of hawk weeds which produce runners (e.g. Hieracium Pilosella); these, 

 when gathered and placed upright, remain quite stifi" and straight, and do not 

 show the slightest bending. When the stems of Glohularia cordifolia or those of 

 the Hairy Genista (Genista pilosa), growing on a rocky ledge, reach over the edge, 

 they do not hang down vertically, as would be the case if their own weight were 

 exclusively the cause of the direction taken, but they skirt along the face of the 

 overhanging rock and remain closely pressed against it. 



The first group of plants with procumbent foliage-stems is perennial; the 

 growing -points of their stems advance over the substratum a little every year, 

 and the new-formed shoot is the continuation of the older portion of the already 



