育苗

1) We have made an enquiry into the effects of "pinching-back" on young mulberry trees in the nursery, as practised in various stages of their growth. For the purpose of comparative study, we divided our nursery into the following sections:? The "Control" Section, where no pinching-back has been practised. Section "A," where the trees were pinched back once in late September while in growth. Section " B," where the trees were pinched back once in August, and then the axillary buds sprouting thereafter were all removed. The growth of stems having thus been checked, the leaves borne by these trees have been much limited in number. Section "C," where the trees were pinched hack once in August, and then only two or three uppermost axillary buds were allowed to grow from each tree. In autumn, the leaves borne by these new stems were collected for September-silkworm-culture. 2) The trees in Section "A," where the pinching-back was practised in autumn, are generally found to be compared favourably with those in the "Control" Section, in the gross weighte respectively of the young trees, the roots, and the stems; in the length of the stems, and in the weight of the stems cut to a certain uniform length; in the diameters of the transverse sections of the stems; etc. On the other hand, the trees in both Sections "B" and "C" are found to be inferior in all these respects to those in the "Control" Section; while the ratio between the diameter of the pith and that of the stem is found to be large in either of these Sections to the same ratio in the "Control" Section. 3) The trees in Section "A," while in the breaking strength and the specific gravity of the stems approximately resembling those in the "Control" Section, have had smaller parts winterkilled. On the other hand, the tree s in Section "B," though having a somewhat smaller breaking strength and smaller specific gravity of the stems, have been least susceptible to winterkilling. Lastly, Section "C" has presented the poorest results, having the smallest breaking strength and specific gravity of the stems, and having had the largest parts winterkilled. 4) As compared with the "Control" Section, Section "A" has been observed to contain almost equal percentages respectively of water, dry matter, ash, and organic matter; whilst Sections "B" and "C" generally contain larger percentages of water and ash and smaller percentages of dry and organic matters. 5) As compared with the "Control" Section, Section "A" contains a more or less smaller percentage of soluble carbohydrates; especially is this the case with the preserved carbohydrates contained in the roots, the proportion of such preserved nutriments markedly tending to be inferior in the trees in this Section. Sections "B" and "C" are both inferior to the "Control" Section in the proportional quantities of the above mentioned constituents, particularly so as regards the preserved carbohydrates contained in the roots. This general tendency in the "treated" Sections may be attributed to the comparative scarcity of foliage resultant from the pinching-back and disbudding. 6) As regards nitrogen compounds, little or no marked difference is noticeable among the four Sections studied: only, Section "B" tends to hold a larger percentage than other Sections of these compounds. Thus, it has been observed that the percent ages of the nitrogen compounds contained in the trees in the four Sections present somewhat different aspects from the percentages of the soluble carbohydrates contained in the same. 7) As regards these constituents and preserved nutrinents contained in the roots and stems, Section "A" generally resembles the "Control" Section, in the absolute quantities of the dry matter, of the ash, and of the organic matter, but tends to be somewhat inferior in the absolute quantities of the soluble carbohydrates and of the nitrogen compounds. Section "B" and "C" are both inferior to the "Control" Section in the absolute quantities of the above mentioned constituents and of the preserved nutriments. 8) As regards the absolute quantities of the same constituents and preserved nutriments contained in the combination of the stems cut to a certain uniform length and of the roots, the results of our enquiry have been identical with the results described under 7).