The diseases and pests of the rubber tree . d vertically with the micropyleuppermost. (e) 50 seeds were planted horizontally, and on theirnarrower side. The results of this experiment are illustrated in Fig. 1 (from the left) is a typical seedling of lot (a) in which48 germinated, all normally. No. 2 represents the seedlingsof lot (6) of which 49 germinated, all normally. No. 3 is aseedling of lot (c), one of 47, all of which were normal,though the seeds were raised above the soil. Nos. 4 and 5are typical of the seedlipgs of lot {d), in which 45 seedsgerminated; 27 of the seedlings had
The diseases and pests of the rubber tree . d vertically with the micropyleuppermost. (e) 50 seeds were planted horizontally, and on theirnarrower side. The results of this experiment are illustrated in Fig. 1 (from the left) is a typical seedling of lot (a) in which48 germinated, all normally. No. 2 represents the seedlingsof lot (6) of which 49 germinated, all normally. No. 3 is aseedling of lot (c), one of 47, all of which were normal,though the seeds were raised above the soil. Nos. 4 and 5are typical of the seedlipgs of lot {d), in which 45 seedsgerminated; 27 of the seedlings had a knee bend, as shownin No. 4, and in 9 others this was accentuated into the shapeof an N, while the remaining 9 formed complete loops asillustrated in No. 5. No. 6 is a representative seedling of lot(e), of which 39 seeds germinated, all normally. Experiment (d) was repeated with 20 seeds ; 15 of these NON-PARASITIC DISEASES 193 germinated, 11 with, simple knee, or N-shaped bends, and4 with complete loops. It would appear, therefore, that. s 3 60 S planting the seed with the micropylar end uppermost favoursthe production of twisted seedlings. 194 THE RUBBER TREE ^^ When the seed germinates, the developing root (radicle)pushes off the circiJar cap which closes the micropyle, andemerges as a white stump, about three or four millimetres indiameter, with a truncate flattened end. As it lengthens,the flattened end becomes slightly conical and its margindevelops a number of minute points. The conical centralpoint is the developing tap root, while the marginal pointsare the developing lateral, or secondary, roots. It is apeculiar feature of Hmea that the secondary roots at firstgrow much more rapidly than the primary, or tap, root, andserve to fix the yoimg plant as the radicle curves downwards. The two seedling leaves (cotyledons) remain within theseed and absorb the food stored up round them. But thestalks of these leaves are lengthened until they project outsidethe seed for a leng
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Keywords: ., bookcentury1900, bookdecade1920, bookidcu3192400285, bookyear1921
