164 EXTERNAL CONFORMATIO.Y OF PLANTS. 



podiacea? is dichotomoiis. In Psilotum tri^netrum all the branches develope uniformly; it 

 is the most regularly developed dichotomy found among vascular plants. In the Lyco- 

 podia the development U much more irregular, but always in such a manner that the 

 bifurcation is conspicuous throughout ; in the Selaginella^, on the other hand, it is gene- 

 rally to be recognised only on the youngest branches, since the bifurcations are developed 

 sympodially, and in fact as scorpioid cymes. This often happens (as in Selag'mella 

 flabellata) in such a manner that the entire outline of a branch consisting of numerous 

 bifurcations assumes a form similar to that of a multipinnate Fern-leaf. The be- 

 ginner who desires to obtain a clear idea of the different modes of development of a 

 system produced from a dichotomous origin, especially the formation of sympodial forms 

 out of dichotomies, could find no better object of study than the Selaginellse which are 

 cultivated in all hot-houses. On the branching of the stem of Ferns and Rhizocarps, 

 reference should be made to the description of the respective classes in Book II. 



The branching always originates monopodially in the stems of Characeae, Equiseta- 

 ceap, and Coniferfie, and even with a racemose development. The branch-systems of 

 Mosses also always proceed from a monopodial origin, but are sometimes developed 

 sympodially (as the innovations of Acrocarpous Mosses beneath the floral organs). It 

 is oiten very irregular, but sometimes occurs in such a manner that much-branched 

 systems of shoots when racemosely developed assume defined outlines, like those of 

 multipinnate leaves (Hylocomium, Thuidium, &c.). 



The branching of Monocotyledons and Dicotyledons is always originally monopodial, 

 but the mode of development of the system is extraordinarily variable ; on the same plant 

 and even on the same branch-system different forms, for example both racemose and 

 cymose, may arise. The peculiarities of the different forms of development are usually 

 very conspicuous in inflorescences, and of many difterent kinds ; and since the attention 

 of botanists has been turned for a long time in this direction, they are not only copiously 

 employed in the description of plants, but also furnished with names, from which those 

 used here in a more general sense are partly borrowed. A more special description of 

 those branch-systems which, in the case of Flowering Plants are called Inflorescences, 

 will follow in the general consideration of Angiosperms in Book II ; here it is only 

 necessary to mention that the forms distinguished as spikes, racemes, and panicles are 

 especially clear examples of the racemose development, while those termed dichasia, 

 cymose umbels (in Euphorbia), and scorpioid and helicoid cymes, and are examples of 

 the sympodial development of monopodial branch-systems. 



Every other form of (vegetative) branching of Flowering Plants may be regarded 

 from the same point of view. The formation of sympodia is not unfrequently brought 

 about by the arrest of the terminal portion or terminal bud of the shoot, while the nearest 

 lateral bud developes all the more vigorously, and appears like a continuation of the 

 mother-shoot, as in Robinia, Gorylus, Cercis, and many other plants ; in the lime the 

 primary stem itself is a sympodium formed in this manner. If the flower-bearing shoots 

 above ground die annually, while the underground portions remain in a living condition, 

 underground sympodia sometimes arise composed of short thick basal portions of 

 numerous larger shoots which have long since died off. This is the case, for instance, in 

 Polygonatum multtflorum, the underground stem of which is known under the name of 

 Solomon's Seal. In Fig. 135 is represented the front portion of one of these under- 

 ground stems, those produced during eight previous years having disappeared. The 

 stem denoted by the number 1866 is the lower portion of the upright aerial shoot bear- 

 ing leaves and lateral flowers, which was in existence in that year ; but this shoot is 

 itself only the terminal part, its much thicker basil portion is denoted in the diagram 

 B as seen from above by ^ + 2 ; the thinner terminal part dies off in the autumn, and at 

 b, b, beneath the numbers 1864 and 1865, are shown the scars which remain behind 

 after the death of the similar earlier terminal parts. The portion here represented 

 of the sympodium thus consists of the three basal portions n,n+\, « ^- 2, of three 

 shoots, each of which unfolded its aerial portion bearing leaves and flowers in the 



