HYMENODICTYON 027 



Germination (Fig. 240, 6-e). Epigeous. On the emergence of the radicle 

 the hypocotyl elongates, carrying above ground the cotyledons enclosed in 

 the testa. On the expansion of the cotyledons the testa usually remains for 

 a time on the end of one of them, ultimately dropping to the ground. 



The seedling (Fig. 240). 



Roots : primary root long, thickening early and becoming very thick in 

 second season, terete, tapering : lateral roots few to numerous, fibrous. Hypo- 

 cotyl distinct from root, 0-3-0-5 in. long, cylindrical, green, minutely pubescent. 

 Cotyledons : petiole up to 0-1 in. long, flattened above : lamina 0-35-0-5 in. 

 by 0-25-0-3 in., foliaceous, ovate, emarginate, entire, glabrous, usually per- 

 sisting till end of fii'st season. Stem erect, minutely pubescent, in fii-st season 

 short, with internodes 0- 1-0-2 in. long; in second season thick, woody, with 

 internodes 0-4-1 in. long. Leaves simple, opposite decussate : stipules (first 

 season) less than 0-1 in. long, triangular, pubescent : petiole (first season) 

 0-1 in. long, pubescent, midrib runnmg prominently down upper side : lamina 

 (first season) 0-8-1-8 in. by 0-6-1 in., sub-rhomboidal or ovate, acute, base 

 tapering, entire, pubescent, venation arcuate, lateral veins 4-6 pairs, midrib 

 often red. 



The seedling develops very slowly above ground during the first season, 

 and under natural conditions also during the second or third seasons, after 

 which, if the plant survives, the growth is more rapid. As a rule a height 

 of not more than 1 or 2 in. is attained during the first season, with not more 

 than three to five pairs of leaves. The underground development, however, is 

 considerable, a long stout taproot being quickly formed ; this may be as much 

 as 1 ft. 6 in. long by the end of the first season. This underground develop- 

 ment, which is common among seedlings of trees characteristic of dry types 

 of forest, is evidently an adaptation for the establishment of the plant before 

 any marked growth in the stem begins. 



The seedling is very sensitive to frost, especially during the first year or 

 two while the plants are small ; in locaHties subject to frost many seedlings 

 are killed outright, while some may shoot up again from the base. Weeds 

 impede the development of seedlings considerably, suppressing and kiUing 

 them if heavy. The seedling is decidedly light-demanding. Growth ceases 

 from November to May ; the leaves turn yellow or reddish and drop in 

 November-December, the plants being leafless from January to May, when 

 the new leaves appear (northern India). 



The following measurements in experimental plots at Dehra Dun give 

 some indication of the rate of growth of young plants : 



Hymenodictyon excelsum : development of seedlings, Dehra Dun. 

 )n under which Height at end of season. 



gfown. 1st season. 2nd season. 3rd season. 4th season, 



ral conditions Maximum ft. 1 in. 

 ery, weeded and 



ired ,, Oft. 1 1 in. Maximum 1 ft. .3 in. 



[cast sowing, irri- 

 A, unweeded ft. 2 in. ft. 3 in.' Killed by weeds in 



3rd season 

 icast sowing, un- 



ated, unweeded Oft. 1 J in. ft. 1 Mn.^ Ditto 



[least sowing, un- 

 ated, weeded ft. 2 in. ft. 4 in.^ 10 in.-2 ft. 4 in. Maximum T) ft. Gin. 



* New shoots from base ; seedlings killed back by frost in previous winter, 



U2 



