668 SCIENTIFIC RECREATIONS.. 



The duration of the stem of a plant is usually the same as of the plant 

 so we have annuals, biennials, and perennials. The substance of the stem 

 determines its character, so we may have it solid, or soft, hollow, tubular, 

 flexible, rigid, or a tough stem. There are fibrous, herbaceous, and juicy 

 stems. They may be directed uprightly, straight, procumbently, arched, or 

 creeping, above, or underground, climbing, clinging, floating, or twining. 



There are many plants with little or no stem deserving the name, as in 

 the onion ; and we must all remember when studying botany that it is not 

 the place where a portion of a plant may be found that constitutes it a root 

 or a stem. The form and structure should be studied, and its purpose in 

 creation. So stems may be underground and roots above it. The root 

 and stem, briefly treated of in the foregoing paragraphs, have certain points 

 of resemblance, inasmuch as both consist of a main or trunk line, so to speak, 

 from which branches diverge as " rootlets " and " twigs " ; and how beautiful 

 the latter are any one can see in a good photograph of a wintry landscape. 

 But stems have nodes and internodes, and roots have not, and this is the great 

 and apparent difference. 



The covering of plant-stems is varied, and many instances of such 

 clothing will occur. We have woolly stems and hairy stems, which develop 

 into thorny ones for thorns are only strong hairs. Spines and stings and 

 prickles defend the stems, and keep rude hands from meddling. We will 

 now cut the stem and see what it is composed of, and how it looks inside. 

 We have only to cut it across and again perpendicularly to find out a great 

 deal about the interior structure of the stems of branching plants (exogens). 



The elder, from which the whistle of our boyish days is fashioned with 

 a penknife, will serve any lad for an illustration. Inside we find what is 

 called " pith," which is cellular tissue. Round this is fibre, and outside is a 

 skin, or the plant-cuticle. We may remark that the tissues of flowering 

 plants are characteristic of the monocotyledonous and the dicotyledonous 

 plants. Of the former we append an illustration, a section of palm-stem, - 

 and we find bundles of vascular tissue dispersed apparently at random 

 amongst the cellular tissue of the parenchyma, or cellular tissue. These 

 stems do not grow by the increase of the existing vascular tissue, but by 

 their new production at the circumference, and so they grow in both 

 directions, laterally and uprightly. These plants belong to the ENDOGENS, 

 and if Indian corn be grown we shall have full opportunity to study the 

 formation. In cutting a fern stem we are familiar with the " oak " pattern 

 of the matter it contains. We have few specimens of endogens in England. 



The dicotyledonous stems are common to our trees and most plants, 

 and may therefore be considered with advantage. The stem consists of the 

 vascular tissue called " pith," and we give an illustration of the cells magni- 

 fied very considerably. The arrow indicates the outward direction (fig. 757). 



We here perceive the vascular bundle proper surrounded by a very 

 large-celled tissue, aa' bef. The almost square cells, aa', form the epider- 

 mis on which follows the less dense cellular tissue of the bark. The latter 



