i6o 



Garden and Forest. 



[Number 215. 



cies with large yellow flowers, which thrives in English rock- 

 gardens ; T. chamaedrys, a taller grower with smaller rose- 

 colorcd flowers, and Artemesia vallesiaca, a very rare and 

 graceful plant, with finely cut ashy gray leaves. Anemone 

 Hepatica was easily recognized by its leaves. Ononis rotundi- 

 folia, a species with large rosy red pea-shaped flowers, and O. 

 Natrix, with large yellow flowers, were conspicuous in sunny 

 spots on banks ; both are good garden-plants in Britain. 

 Kew. Geo. Nicholson. 



Serotinous Pines. 



OF the thirty-seven species of Pines found within the borders 

 of the United States, a small group are somewhat peculiar 

 in the development and persistence of their cones. As is well 

 known, most Pines mature their cones in about two years — 

 i. e., the incipient cones of one spring become fully developed 

 in the fall of the second year. The period of ripening usually 

 begins about October, and if the weather be dry and warm the 

 cones soon afterward begin to open and the seeds to be lib- 

 erated. From then on till spring the cone-scales continue to 

 open and close under the alternating influence of warmth and 

 moisture, and with one or two northern species a large quan- 

 tity of seed is liberated only after the snow has departed and 

 the sun is again sufficiently warm to thoroughly open the 

 cones. 



The Pines having their leaves in fascicles of five, a group in 

 which the White Pines naturally fall, are doubtless the least 

 tardy in shedding their seeds, as they are least tenacious in 

 holding their cones ; few, if any, seeds or cones survive the 

 shedding process which nature subjects them to during the 

 first winter. 



In the group Taeda, two and three-leaved Pines, comprising 

 about twenty species, mostly southern and western, it is not 

 uncommon, however, to find cones persisting on the trees for 

 eight to ten years. The most striking examples of this pecu- 

 liarity are seen in the following species : Pinus contorta, P. 

 Murrayana, P. muricata, P. tuberculata, P. insignis, P. Virgini- 

 ana, P. clausa, P. rigida, P. pungens and P. serotina. Among 

 these species may be specially mentioned P. clausa, P. sero- 

 tina, P. tuberculata and P. insignis as additionally remarkable 

 for retaining their seeds long after the cones are mature. 



Michaux was doubtless the first to observe that the Pond 

 Pine (P. serotina) of the southern states matures its cones in 

 two years, but does not liberate its seeds till the third or even 

 fourth year. The closely allied Pitch Pine (P. rigida) of the north 

 Atlantic region, though producing less commonly serotinous 

 cones, frequently retains its seeds for a considerable time after 

 the cones are mature. Latest, perhaps, among the discoveries 

 of eastern serotinous Pines is the Florida Spruce Pine (P. 

 clausa), in which the seeds are retained at least three or four 

 years. The cones of some individuals of this species, an il- 

 lustration of which is given on page 161, are not without excep- 

 tion in sometimes opening at or soon after maturity (Fig. 24, c), 

 while others ordinarily remain closed for a longer period ; 

 occasionally cones are found in which the. seeds ten years 

 old have apparently not been liberated. 



Of the eastern serotinous species the Florida Spruce Pine is 

 moreover most interesting in the persistency with which it re- 

 tains its cones. They are so strongly attached by a tough 

 woody columella that the growing tissue of the trunk or branch 

 rarely forces the cones off, but in time commonly envelops 

 them, as seen in .^, Fig. 24. Tfie important stages of persistence 

 following the mature open cone (c), to the deeply-imbedded 

 cones (/i), are successively illustrated in (;,/and^of the figure. 

 It may be of interest here to recall the note published twelve 

 years ago by Dr. Engelmann (Bot. Gazette, v., 62, 63) on the vi- 

 tality of seeds from the serotinous cones of P. Murrayana, a Pa- 

 cific Coast species. The cones were collected in Colorado in 

 1875, and after being kept in a dry garret for about five years 

 ' were sent to Professor Sargent to experiment with as to their ger- 

 minating pov/er. Seed from cones five years old did not germi- 

 nate. Seeds still older germinated and grew up, as follows : 

 One out of four six-year-old seeds, one out of three seven-year- 

 old, one out of eleven eight-year-old, one out of six nine-year- 

 old. Seeds from cones ten and eleven years old did not 

 germinate, although such seeds were perfectly sweet and ap- 

 parently sound. 



Dr. Engelmann remarks that the above result was not con- 

 sidered satisfactory; his own opinion, however, being that 

 the result was highly satisfactory, showing that seed in cones 

 five to nine years old retained their vitality, while seed from 

 those over nine tailed to grow. 



These experiments, doubtless, indicate clearly enough that 

 the life of serotinous Pine-seeds may be trebled, if not quad- 



rupled, by being kept in the cones, as compared with shelled 

 seed preserved under the same dry and certainly most un- 

 favorable conditions, it being well known that the germinating 

 power of shelled seed rarely endures longer than two or three 

 years, and usually fails for any considerable per cent, of ger- 

 mination even earlier than this. Why the seed from five-year- 

 old cones did not germinate is not clear, for it is not probable 

 that the younger seed should possess the greatest vitality. 

 The whole subject suggests the need of experiment on the 

 length of time which may elapse before these cones open and 

 during which the seeds retain their vitality. 



The degree of heat and moisture to which the cones are 

 subjected doubtless has much to do with the quesfion of early 

 or late opening ; this in turn being determined by the season. 

 The comparative effects of these elements are illustrated in 

 the behavior of ripe cones of P. clausa subjected to different 

 degrees of heat. Cones left out-of-doors during one season 

 have not opened, but those kept in a covered box in a room 

 with temperature ranging from sixty-eight to ninety degrees, 

 Fahrenheit, opened within two months {c. Fig. 24), while cones 

 five to seven years old have not opened under either set of 

 conditions. Cones of P. serotina have also behaved similarly 

 under the same conditions. 



But it is a noticeable fact with almost all serotinous species 

 that a few cones may be found on nearly every individual 

 which open at or soon after maturity, this early opening occur- 

 ring most frequently on the south and east sides of the crown ; 

 occasional opening of this kind may be observed for two to 

 three ySars after maturity, so that all individuals and species 

 of this class cannot be said to be uniformly serotinous until at 

 least some seeds are shed. The amount of seed liberated at 

 one period of opening is often quite small, the majority of the 

 cones appearing to remain closed. 



In seeking for the special economy which nature seems to 

 aim at in imposing upon certain species of Pines the necessity 

 of keeping their seeds over indefinitely, or the mechanical 

 hindrance to shedding them at maturity, it would be interest- 

 ing to discover how far in reality this peculiar ability or dis- 

 ability is of advantage in perpetuating the species. It would 

 seem quite improbable that for a most perfect germination 

 the seeds should thus be housed for several years before being- 

 allowed to escape, as if by retenfion it were necessary for the 

 seeds to undergo some as yet unknown physiological change, 

 such as that required by certain fungus spores which are 

 unable to germinate until they have passed a winter in the 

 open air. For the seeds of P. clausa this is certainly not neces- 

 sary, as those extracted from mature cones two years old 

 germinated immediately. 



There is very little chance of the most persistent serofinous 

 cones reaching the ground, in the ordinary course of events, 

 within eight to ten years, and if they did, they would be likely 

 to open more tardily still ; and seed so confined would doubt- 

 less become spoiled before the cones were sufficiently de- 

 cayed to liberate it. 



With the exception, perhaps, of P. serofina, our serotinous 

 Pines naturally inhabit dry and sometimes nearly arid locali- 

 ties. It may be, therefore, that some advantage accrues to 

 such species in not being able to lose all their seed at once ; 

 the actual process of serotinous species being to give up only 

 a few seeds at a time, and thus make the most of their chances 

 to secure conditions favorable for germinafion. Many other 

 Pines not strictly serotinous, inhabiting similar dry and arid 

 regions, seem to follow the same plan of tardy shedding of 

 seed. 



The little-known Florida Pinus clausa is geographically 

 somewhat confined in Florida, ranging only from the western 

 border of the state southward along the coast, usually not over 

 thirty miles inland, to the Cedar Keys, where Professor Sargent 

 found it growing quite abundantly. It occurs also on the At- 

 lantic side, south of St. Augustine, here occupying only a nar- 

 row ridge of sandy upland as far south as latitude twenty-nine 

 degrees. For the most part it seems to take kindly to the 

 pure sand wastes of the Florida coast, and is here rarely ever 

 more than fifteen to thirty, occasionally forty, feet in height, 

 with a diameter under twelve inches, and branches often coming 

 down quite to the ground. It is not uncommon along these sand- 

 dunes to see numbers of these trees bent over or uprooted by 

 the strong autumnal gales, the yielding sand not affording suf- 

 ficient support for the roots. On higher ridges and uplands, 

 where the sandy soil is richer from an admixture of clayey 

 marl, it becomes a much larger tree, and is associated with 

 deciduous-leafed trees (Hickories, Oaks and Magnolias), here 

 attaining a height of fifty to seventy feet and over, with a trunk- 

 diameter of more than eighteen inches. In the region of Hali- 

 fax Bay finely developed specimens of this Pine are still to be 



