Fig. 749. 



ORGANS OF REPRODUCTION. 



Fig. 750. Fig. 751. 



339 



Fig. 752. 



Fig. 749. The embryo of the Almond 

 {Amygdalus communis) from which 

 one of the cotyledons has been re- 

 moved, c. Tlie cotyledon which has 

 been left. r. Radicle, g. Plumule. 

 *. Tigelle or caulicule. c'. Scar left 



by the removal of the other cotyledon. Fig. 750. Vertical section of the 



embryo of a species of if irfl?a. c'. Large cotyledon, c. Small cotyledon. 



g. Plumule, r. Radicle. Fig. 751. Vertical section of the embryo of 



Carapa guianensis, showing the almost complete union of the cotyle- 

 dons, the line, c, only dividing them. r. Radicle, gr. Plumule. Fig. 



752. The embrj'o of Pekea butyrosa. t. Large tigelle. c. Rudimentary 

 cotyledons. 



The cotyledons are sometimes altogether ahsent, as in Cuscuta. 

 At other times their number is increased, and this may either 

 occur as an irregular character, or as a regular condition, as in 

 many Coniferae {fig. 753, c), where -we frequently find six, nine, 

 or even fifteen cotyledons ; hence such embr}- os have been termed 

 polycotylcdonous. It seems, however, that this appearance of a 

 larger n\imber of cotyledons than is usual in Dicotyledonous 

 Plants, arises from the normal number becoming divided down 

 to their base into segments. In all cases where the number 

 of cotyledons is thus increased, they are arranged in a whorl 



Fig. 754. 



(%. 753) 



The cotyledons are usually 

 thick and fleshy, as those of 

 the Bean and Almond {fig. 

 749), in which case they are 

 termed fleshy ; at other times 

 they are thin and leaf-like, as 

 in the Lime {fig. 744), when 

 they are said to be foUaceous. 

 The foliaceous cotyledons are 

 frequently provided ■svith veins, 

 and stomata may be also some- 

 times observed on their epider- 

 mis : these parts are rarely to 

 be found in fleshy cotyledons. 

 Fleshy cotyledons serve a simi- 

 lar purpose to the albumen, by acting as a reservoir of nutri- 

 tious matters for the use of the young plant during germina- 

 tion ; hence, when the albumen is absent, the cotyledons are 

 generally proportionately increased in size. 

 z 2 



Fig. 753. Polycotylc- 

 donous embryo of a 

 Pmus beginning to 

 germinate, c. Coty- 

 ledons, r. Radicle. 



t. Tigelle. Fig. 754. 



The embryo of Gera- 

 nium molle. c. Coty- 

 ledons, each of which 

 is furnished with a pe- 

 tiole, p. r. Radicle. 



