94 



COTYLEDONS. 



Fig. 123. 



COTYLEDON. 



40. The plumule (figs. 121, c, and 125, d) or young stem is 

 sometimes scarcely visible before germination ; at other times it 

 is as long as the radicle with which it is inferioriy continuous : 

 by development it becomes elongated in a direction contrary to 

 that of the root, and consequently it always tends to rise. We 

 distinguish in it two parts, namely: the stemmule and \he gemmule, 

 situate one above and the other below the coty'ledons. 



41. The coty'ledons are lateral appendages 

 which represent the first leaves (fig. 123). They 

 are almost always thick and fleshy in plants un- 

 provided with albumen, but thin and membranous 

 in endospermatic seeds. Their use seems to be to 

 furnish the young plant with the first alimentary 

 matter, and their number is various; sometimes 

 there is but one and at others there are two ot 

 more. 



42. Plants whose seeds contain only a single 

 coty'ledon, are named monocot.y' ledons (from the Greek, monos, 

 single, and kotuledbn, seed-lobe) ; those whose seeds contain two 

 or more coty'ledons, are named dicotyledons (from the Greek, dis t 

 iwo, and kotuledon, seed-lobe). 



The annexed figure (124) 



represents the section of a 



seed of a monocoty'ledon in 



process of germination, 



showing the perisperm (d) ; 



the summit of the single 



coty'ledon (6) ; the base of 



the coty'ledon, forming a 



sort of tube (c) ; at the lower 



part of the base we see the 



plumule (d), which sets upon 



the radicle (e). 



Figure 125 represents the same seed, further 

 advanced in germination, after the appearance 

 of the plumule or young stem (d]. 



43. When the seeds are ripe or a short time afterwards, they 

 separate from the plant ; sometimes the fruit opens spontaneously 

 to permit their escape; at other times they are detached without 



Explanation of Fig. 123. A seed in process of germination : c, base of 

 Ihe cotyledon. 



40. What is the plumule ? (Plumule : from the Latin plumula, a little 

 feather.) 



41. What are coty'ledons ? What is their use ? 



42. What is meant by a monocoty'ledon ? What is dicoty'ledon ? 



43. How are setda naturally distributed ? 



--C 



Fig. 124. 



COTYLEDON. 



Fig. 125. 

 COTYLEDON 



