The Development of Urginea "Families"
One of the names used for the plant in various places in the Mediterranean area is “the bulb of the dead” (according to HaReubeni 1941). Every one who passed near the closed Golden (Mercy) Gate of Old Jerusalem, has seen the squill field beside the Muslim cemetery (Figs. 9.2.1-9.2.3). How does the leaf circle of Fig. 9.2.3 become filled up, and how is it related to a single individual as presented in Figs. [usefulplantsi1 9.1.4] and 9.2.3? This question bothered me for some time. I studied a squill with two leaf rosettes (Fig. 9.2.4). I removed the dry brown outer scales which are old leaf-bases. Years previously they stored photosynthesis products and the plant used them later. The scales were attached to the stem which looks round with circular depressions.
The Hebrew term used for the bulb’s stem is “the bulb’s cake”. The bulb in Fig. 9.2.5 displayed a hidden depression between the two leaf rosettes; its nature was understood later when leaf-base removal took place (Fig. 9.2.6). Among the two leaf groups there was a thin, narrow brown scale (Fig. 9.2.6). The latter was the base of an old inflorescence. The removal of all the young leaves exposed the two apical meristems (Fig. 9.2.6). What caused the splitting of the bulb’s apical meristem into two? As long as the mother bulb (the one with two buds or two apical meristem) did not bloom, the single stem produced a leaf rosette in winter, stored photosynthesis products at the leaf bases and lost its drying lamina toward summer. Those bulbs that were big enough and ready to bloom terminated their apical meristem, which changed into an embryonic inflorescence in summer.
The lateral buds, each in the axile of a leaf base, did not develop because of the “apical dominance.” The apical bud produces hormones which suppress the growth of the lateral buds. Blooming in August-September the inflorescence terminates the activity of the apical bud. When visiting the Lasithi Valley in Crete in 1983, I saw squills that bloomed when the leaves were still green-yellow. Visiting the same place in 2000, the squill behaved as in Israel and bloomed with totally dry leaves. I therefore wrote a note for myself that the squill behaves according to the summer weather before blooming.
One of the questions I am often asked, concerning the squill, is how the plant “knows” when to bloom. I do not know the answer from any experimental study, but I am ready to open my book of assumptions: The bulb scale is the lower part of the leaf and as shown in Fig. 9.2.8/left, it is thickened and stores food and moisture. Above the number 10 of the scale bar is the dry brown part of the storing scale. From this point upward was the green lamina of the leaf. The latter dried and fell off during the summer. The top of the scale is close to the surface of the soil and may absorb solar radiation which can be sensed by the plant, via chemical changes in the leaf cells, and leads to flowering. Thus, the top of the scale may be part of a “tool” for measuring the length of the day. The scale is thickened between the numbers 1 through 6 on the scale bar of Fig. 9.2.8/right.
Once the apical bud of the bulb has turned into an inflorescence it no longer suppresses the lateral buds and two of them start to develop within one bulb (Figs. 9.2.5, 9.2.6). An advanced stage is presented in Fig. 9.2.9. The storing scales of the two daughter bulbs, which had a straight plane in their contact zone, grow and thicken. The resulting pressure leads to a tearing of the subtending scales (Fig. 9.2.9/left). The two bulbs still share the “bulb cake” and the part where roots are (Fig. 9.2.10) is in the final splitting stage. They may soon become two independent bulbs. As the years pass, they will reach the stage displayed in Fig. 9.2.3, by the process shown in Fig. 9.2.11.
When visiting “Little Petra,” nearly 5 km north of Petra and Wadi Musa, I enjoyed the assistance I got from goats in the bulb splitting story. The sandy soil that is trampled by the large goat herds is easily eroded by wind and exposes the “squill bulb families” (Figs. 9.2.12, 9.2.13). The adult bulb (Fig. 9.2.13/right) containing two daughter bulbs, will soon split into two independent bulbs. The small bulbs in Fig. 9.2.13/left seem to be four or five buds that started to grow as a result of damage to the apical bud of their mother bulb. The squill “family” in Fig. 9.2.14 develops leaves while the flowering stalks of the previous year have not yet dried up. The leaves of the present year developed beside the previous year’s inflorescence (this situation is clearly seen in Figs. 9.2.11 and at the left side of Fig. 9.2.14). All the leaves of the “squill family” seen in Fig. 9.2.15 are the offspring of one individual bulb planted many years ago.